P — pa pe pf ph pi pl pn po pr ps pt pu py pw pc pm pd
phaeton |ˈfeɪtən| — large open car seating four with folding top
phage |feɪdʒ| — a virus that is parasitic (reproduces itself) in bacteria
phagocyte |ˈfæɡəsaɪt| — a cell that engulfs and digests debris and invading microorganisms
phalange |fəˈlændʒ| — A right-wing Lebanese paramilitary movement based somewhat on the Spanish Falange
phalanges |fəˈlændʒɪz| — plural form of phalange
phalanstery |ˈfælʌnˌsteriː| — An association or community organized on the plan of Charles Fourier, with living space divided hierarchically and higher pay for those carrying out unpopular tasks.
phalanx |ˈfælæŋks| — any of the bones of the fingers or toes
phalli |ˈfælaɪ| — plural form of phallus
phallic |ˈfælɪk| — resembling or being a phallus
phallus |ˈfæləs| — genus of fungi having the cap or pileus hanging free around the stem
phanerogam |ˈfanərəˌɡam| — plant that reproduces by means of seeds not spores
phanerogamic |ˌfænərəʊˈɡæmɪk| — (botany) That reproduces via seeds (rather than spores)
phanerogamous — phanerogamic
phantasm |ˈfæntæzəm| — a ghostly appearing figure
phantasmagoria |ˌfæntæzməˈɡɔːrɪə| — a constantly changing medley of real or imagined images (as in a dream)
phantasmagoric |fænˌtæzmʌˈɡɔːrɪk| — characterized by fantastic imagery and incongruous juxtapositions
phantasmal |fænˈtæzməl| — resembling or characteristic of a phantom
phantasy |ˈfæntəsɪ| — something many people believe that is false
phantom |ˈfæntəm| — a ghostly appearing figure
Pharaoh |ˈferəʊ| — the title of the ancient Egyptian kings
Pharisaic |ˌfærɪˈseɪɪk| — excessively or hypocritically pious
Pharisaical |ˌfærɪˈseɪɪkəl| — excessively or hypocritically pious
Pharisaism |ˈfærəˌseˌɪzəm| — The doctrines and practices, or the character and spirit, of the Pharisees
Pharisee |ˈfærɪsiː| — a self-righteous or sanctimonious person
pharmaceutic — drug or medicine that is prepared or dispensed in pharmacies and used in medical treatment
pharmaceutical |ˌfɑːrməˈsuːtɪkl| — drug or medicine that is prepared or dispensed in pharmacies and used in medical treatment
pharmaceutics |fɑːrməˈsuːtɪks| — the art and science of preparing and dispensing drugs and medicines,
pharmaceutist |ˌfɑːməˈsjuːtɪst| — (dated) One skilled in pharmacy; a druggist.
pharmacist |ˈfɑːrməsɪst| — a health professional trained in the art of preparing and dispensing drugs
pharmacological |ˌfɑːrməkəˈlɑːdʒɪkəl| — of or relating to pharmacology
pharmacologist |ˌfɑːrməˈkɑːləˌdʒɪst| — someone trained in the science of drugs (their composition and uses and effects)
pharmacology |ˌfɑːrməˈkɑːlədʒɪ| — the science or study of drugs: their preparation and properties and uses and effects
pharmacopoeia |ˌfɑːrməkəˈpiːə| — a collection or stock of drugs
pharmacy |ˈfɑːrməsɪ| — the art and science of preparing and dispensing drugs and medicines,
pharos |ˈfe(ə)rɒs| — a tower with a light that gives warning of shoals to passing ships
pharyngeal |fəˈrɪndʒɪəl| — a consonant articulated in the back of the mouth or throat
pharyngitis |ˌfærɪnˈdʒaɪtɪs| — inflammation of the fauces and pharynx
pharynx |ˈfærɪŋks| — the passage to the stomach and lungs; in the front part of the neck below the chin and above the collarbone
phase |feɪz| — any distinct time period in a sequence of events
phase-out |ˈfeɪˌzɑːwt| — the act or instance of a planned discontinuation
phased |ˈfeɪzd| — simple past tense and past participle of phase
phasic |ˈfeɪzɪk| — Of or relating to phase
pheasant |ˈfeznt| — large long-tailed gallinaceous bird native to the Old World but introduced elsewhere
phenix |ˈfenɪks| — Archaic spelling of phoenix.
phenol |ˈfiːnɔːl| — any of a class of weakly acidic organic compounds; molecule contains one or more hydroxyl groups
phenology |fəˈnɑːlədʒɪ| — (biology) The study of the effect of climate on periodic biological phenomena.
phenomena |fəˈnɑːmənə| — Plural form of phenomenon.
phenomenal |fəˈnɑːmɪnl| — exceedingly or unbelievably great
phenomenalism |fɪˈnɒmɪn(ə)lɪz(ə)m| — (philosophy) The doctrine that physical objects exist only as perceptual phenomena or sensory stimuli
phenomenological |fɪˌnɒmɪˈnɒlədʒɪ| — (philosophy) Of or relating to phenomenology, or consistent with the principles of phenomenology.
phenomenology |fɪˌnɑːməˈnɑːlədʒɪ| — a philosophical doctrine proposed by Edmund Husserl based on the study of human experience in which considerations of objective reality are not taken into account
phenomenon |fəˈnɑːmɪnən| — any state or process known through the senses rather than by intuition or reasoning
phenotype |ˈfiːnətaɪp| — what an organism looks like as a consequence of the interaction of its genotype and the environment
phenotypic |ˌfɪnəˈtɪpɪk| — of or relating to or constituting a phenotype
pheromone |ˈferəməʊn| — a chemical substance secreted externally by some animals (especially insects) that influences the physiology or behavior of other animals of the same species
phew |fjuː| — Used to show relief, fatigue, surprise, or disgust.
phi |faɪ| — the 21st letter of the Greek alphabet
phial |ˈfaɪəl| — a small bottle that contains a drug (especially a sealed sterile container for injection by needle)
philander |fəˈlandər| — have amorous affairs; of men
philanderer |fɪˈlændərər| — a man who likes many women and has short sexual relationships with them
philandering |ˌfaɪˈlændərɪŋ| — Present participle of philander.
philanthrope |ˈfɪlənˌθrəʊp| — (archaic) A philanthropist.
philanthropic |ˌfɪlənˈθrɑːpɪk| — generous in assistance to the poor
philanthropical — Of or pertaining to philanthropy; characterized by philanthropy; loving or helping mankind; as, a philanthropic enterprise.
philanthropist |fɪˈlænθrəpɪst| — someone who makes charitable donations intended to increase human well-being
philanthropy |fɪˈlænθrəpɪ| — voluntary promotion of human welfare
philatelic |ˌfɪləˈtelɪk| — of or relating to philately or of interest to philatelists
philatelist |fiːˈlætəlɪst| — a collector and student of postage stamps
philately |fɪˈlætəlɪ| — the collection and study of postage stamps
philharmonic |ˌfɪlərˈmɑːnɪk| — a large orchestra; can perform symphonies
philhellenic |ˌfɪlheˈliːnɪk| — characterized by a love of Greece and Grecian things
philippic |fəˈlɪpɪk| — a speech of violent denunciation
Philippine |ˈfɪlɪpiːn| — official language of the Philippines; based on Tagalog; draws its lexicon from other Philippine languages
Philistine |ˈfɪlɪstiːn| — a person who is uninterested in intellectual pursuits
Philistinism |ˈfɪlɪstɪnɪzm| — a desire for wealth and material possessions with little interest in ethical or spiritual matters
philogynist |fɪˈlɑːdʒənɪst| — someone who is fond of women as a group
philologic — philological
philological |ˌfɪləˈlɒdʒɪkəl| — of or relating to or dealing with philology
philologist |fɪˈlɒlədʒɪst| — a humanist specializing in classical scholarship
philology |fɪˈlɑːlədʒɪ| — the humanistic study of language and literature
Philomel |ˈfɪləmel| — (poetic) The nightingale.
philoprogenitive |fɪləʊprəʊˈdʒenɪtɪv| — Prolific, or producing many offspring.
philosopher |fəˈlɑːsəfər| — a specialist in philosophy
philosophic |ˌfɪləˈsɑːfɪk| — characterized by the attitude of a philosopher; meeting trouble with level-headed detachment
philosophical |ˌfɪləˈsɑːfɪkl| — characterized by the attitude of a philosopher; meeting trouble with level-headed detachment
philosophically |ˌfɪləˈsɑːfɪkəlɪ| — in a philosophic manner
philosophize |fəˈlɑːsəfaɪz| — reason philosophically
philosophy |fəˈlɑːsəfɪ| — a belief (or system of beliefs) accepted as authoritative by some group or school
philter — a drink credited with magical power; can make the one who takes it love the one who gave it
philtre |ˈfɪltər| — a drink credited with magical power; can make the one who takes it love the one who gave it
phiz |fɪz| — English illustrator of several of Dickens' novels (1815-1882)
phlebitis |fləˈbaɪtɪs| — inflammation of a vein (usually in the legs)
phlebotomize |flɪˈbɑːtəˌmaɪz| — draw blood
phlebotomy |fləˈbɑːtəmɪ| — surgical incision into a vein; used to treat hemochromatosis
phlegm |flem| — apathy demonstrated by an absence of emotional reactions
phlegmatic |fleɡˈmætɪk| — showing little emotion
phlegmatical — showing little emotion
phlegmon |ˈfleɡmɒn| — A solid mass formed by inflamed connective tissue, such as forms around an appendix in appendicitis.
phloem |ˈfləʊem| — (botany) tissue that conducts synthesized food substances (e.g., from leaves) to parts where needed; consists primarily of sieve tubes
phlogistic |fləˈdʒɪstɪk| — Pertaining to phlogiston.
phlogiston |fləˈdʒɪstən| — a hypothetical substance once believed to be present in all combustible materials and to be released during burning
phlox |flɑːks| — any polemoniaceous plant of the genus Phlox; chiefly North American; cultivated for their clusters of flowers
phobia |ˈfəʊbɪə| — an anxiety disorder characterized by extreme and irrational fear of simple things or social situations
Phoebe |ˈfiːbɪ| — the cardinal number that is the sum of four and one
Phoebus |ˈfiːbəs| — (Greek mythology) Greek god of light; god of prophecy and poetry and music and healing; son of Zeus and Leto; twin brother of Artemis
Phoenician |fəˈniːʃn| — a member of an ancient Semitic people who dominated trade in the first millennium B.C.
phoenix |ˈfiːnɪks| — the state capital and largest city located in south central Arizona; situated in a former desert that has become a prosperous agricultural area thanks to irrigation
phonal |ˈfəʊnəl| — Of or relating to the voice.
phone |fəʊn| — electronic equipment that converts sound into electrical signals that can be transmitted over distances and then converts received signals back into sounds
phoneme |ˈfəʊniːm| — (linguistics) one of a small set of speech sounds that are distinguished by the speakers of a particular language
phonemic |fəˈniːmɪk| — of or relating to phonemes of a particular language
phonetic |fəˈnetɪk| — of or relating to speech sounds
phonetically |fəˈnetɪkəlɪ| — by phonetics
phonetician |ˌfəʊnəˈtɪʃən| — a specialist in phonetics
phoneticize |fəʊˈnetɪsaɪz| — to spell by phonetic script
phonetics |fəˈnetɪks| — the branch of acoustics concerned with speech processes including its production and perception and acoustic analysis
phonetist |ˈfəʊnɪtɪst| — One versed in phonetics; a phonologist.
phoney |ˈfəʊnɪ| — a person who professes beliefs and opinions that he or she does not hold in order to conceal his or her real feelings or motives
phonic |ˈfɑːnɪk| — pertaining to the phonic method of teaching reading
phonics |ˈfɑːnɪks| — teaching reading by training beginners to associate letters with their sound values
phonogram |ˈfəʊnəɡræm| — any written symbol standing for a sound or syllable or morpheme or word
phonograph |ˈfəʊnəɡræf| — machine in which rotating records cause a stylus to vibrate and the vibrations are amplified acoustically or electronically
phonographic |ˌfəʊnəˈɡræfɪk| — of or relating to phonography or to a phonograph
phonography |fəʊˈnɑːɡrəfiː| — the transcription of speech using symbols
phonologic |ˌfəʊnəˈlɒdʒɪk| — of or relating to phonology
phonological |ˌfəʊnəˈlɑːdʒɪkəl| — of or relating to phonology
phonology |fəˈnɑːlədʒɪ| — the study of the sound system of a given language and the analysis and classification of its phonemes
phonometer |fəˈnɑːmɪtər| — An instrument for measuring sounds.
phonoscope |ˈfəʊnəskəʊp| — a device that shows an image representing the acoustical properties of a musical instrument etc.
phony |ˈfəʊnɪ| — a person who professes beliefs and opinions that he or she does not hold in order to conceal his or her real feelings or motives
phosgene |ˈfɑːzdʒiːn| — a colorless poisonous gas that smells like new-mown hay; used in chemical warfare
phosphate |ˈfɑːsfeɪt| — a salt of phosphoric acid
phosphide |ˈfɑːsfaɪd| — (chemistry) Any binary compound of phosphorus, especially one in oxidation state −3.
phosphite |ˈfɑːsfaɪt| — (chemistry) any salt or ester of phosphorous acid
Phosphor |ˈfɑːsˌfɔːr| — a synthetic substance that is fluorescent or phosphorescent; used to coat the screens of cathode ray tubes
phosphor-bronze |ˈfɒsfəbrɒnz| — Any alloy of copper with 3.5 to 10% tin and up to 1% phosphorus, notable for toughness, strength, low coefficient of friction, and fine grain.
phosphorate |ˈfɑːsfəˌreɪt| — to combine or treat with phosphorus; to phosphorize
phosphoresce |ˌfɑːsfəˈres| — to exhibit phosphorescence
phosphorescence |ˌfɑːsfəˈresns| — a fluorescence that persists after the bombarding radiation has ceased
phosphorescent |ˌfɑsfəˈresənt| — emitting light without appreciable heat as by slow oxidation of phosphorous
phosphoric |ˈfɑːsfərɪk| — containing or characteristic of phosphorus
phosphorite |ˈfɑːsfəˌraɪt| — (mineralogy) a sedimentary rock rich in phosphate minerals such as apatite
phosphorous |ˈfɑːsfərəs| — containing or characteristic of phosphorus
phosphorus |ˈfɑːsfərəs| — a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
phot |fɑːt| — a unit of illumination equal to 1 lumen per square centimeter; 10,000 phots equal 1 lux
photic |ˈfəʊtɪk| — of or relating to or caused by light
photo |ˈfəʊtəʊ| — a representation of a person or scene in the form of a print or transparent slide or in digital format
photoactive |ˌfəʊtəʊˈæktɪv| — Able to convert the energy of light into electricity via photoelectricity
photobiotic |ˌfəʊtəʊbaɪˈɑːtɪk| — (biology) that depends on light for life and growth
photocell |ˈfəʊtəʊsel| — a transducer used to detect and measure light and other radiations
photochemical |ˌfəʊtəʊˈkemɪkl| — of or relating to or produced by the effects of light on chemical systems
photochemistry |ˌfəʊtəʊˈkemɪstriː| — branch of chemistry that deals with the chemical action of light
photochromic |ˌfəʊtə(ʊ)ˈkrəʊmɪk| — of, related to, or produced by photochromism
photochromy |ˈfəʊtəkrəʊmɪ| — The art or process of reproducing colours by photography.
photoconductivity |fəʊtəʊˌˌkɑːndəkˈtɪvɪtiː| — change in the electrical conductivity of a substance as a result of absorbing electromagnetic radiation
photocopy |ˈfəʊtəʊkɑːpɪ| — a photographic copy of written or printed or graphic work
photoelectric |ˌfəʊtəʊɪˈlektrɪk| — of or pertaining to photoelectricity
photoelectrical — of or pertaining to photoelectricity
photoelectricity |ˈfəʊtəʊˌɪlekˈtrɪsɪtɪ| — electricity generated by light or affected by light
photoengrave — To make a photoengraving of an image
photoengraving — an engraving used to reproduce an illustration
photogenic |ˌfəʊtəʊˈdʒenɪk| — looking attractive in photographs
photograph |ˈfəʊtəɡræf| — a representation of a person or scene in the form of a print or transparent slide or in digital format
photographer |fəˈtɑːɡrəfər| — someone who takes photographs professionally
photographic |ˌfəʊtəˈɡræfɪk| — representing people or nature with the exactness and fidelity of a photograph
photography |fəˈtɑːɡrəfɪ| — the act of taking and printing photographs
photogravure |ˌfəʊtəɡrəˈvjʊər| — printing from an intaglio plate prepared by photographic methods
photojournalism |ˌfəʊtəʊˈdʒɜːrnəlɪzəm| — journalism that presents a story primarily through the use of pictures
photolithography |ˌfəʊtəʊlɪˈθɒɡrəfɪ| — a planographic printing process using plates made from a photographic image
photolysis |fəʊˈtɑːlɪsɪs| — (chemistry) Any chemical reaction in which a compound is decomposed after absorbing a photon
photomechanical |fəʊtəʊməˈkænɪkəl| — of or relating to or involving various methods of using photography to make plates for printing
photomechanics |ˌfəʊtəʊmɪˈkænɪks| — the process whereby printing surfaces (plates or cylinders) are produced by photographic methods
photometer |fəʊˈtɒmɪtə| — measuring instrument for measuring the luminous intensity of a source by comparing it (visually or photoelectrically) with a standard source
photometric |ˌfəʊtəʊˈmetriːk| — of or relating to photometry
photometrical — of or relating to photometry
photometry |fəʊˈtɑːmɪtriː| — measurement of the properties of light (especially luminous intensity)
photomicrograph |fəʊtəʊˈmaɪkrəˌˌɡræf| — a photograph taken with the help of a microscope
photomicrography |ˌfəʊtəʊmaɪˈkrɒɡrəfɪ| — (photography) photography using a microscope
photomontage |ˌfəʊtəʊmɑːnˈtɑːʒ| — a montage that uses photographic images
photon |ˈfəʊtɑːn| — a quantum of electromagnetic radiation; an elementary particle that is its own antiparticle
photonic — of, or relating to photons or to photonics
photophilous — Thriving in the presence of light.
photophobia |fəʊtəˈfəʊbiːə| — a morbid fear of light
photoplay |ˈfəʊtəˌpleɪ| — a theatrical play that has been filmed for showing as a movie.
photosensitive |ˌfəʊtəʊˈsensətɪv| — sensitive to visible light
photosensitivity — sensitivity to the action of radiant energy
photosphere |ˈfəʊtəsfiːr| — the intensely luminous surface of a star (especially the sun)
photostat |ˈfəʊtəstæt| — a photocopy made on a Photostat machine
photosynthesis |ˌfəʊtəʊˈsɪnθəsɪs| — synthesis of compounds with the aid of radiant energy (especially in plants)
photosynthetic — relating to or using or formed by photosynthesis
phototelegraphy |fəʊtəʊtəˈleɡrəfiː| — The fax system
phototherapy |ˈfəʊtəʊˈθerəpɪ| — the use of strong light to treat acne or hyperbilirubinemia of the newborn
phototube |ˈfəʊtəʊˈtjuːb| — A gas-filled electron tube that has a photosensitive cathode
phototype |ˈfəʊtəˌtaɪp| — A metal printing block, used in the photogravure process
photovoltaic |ˌfəʊtəʊvɒlˈteɪɪk| — producing a voltage when exposed to radiant energy (especially light)
photozincography |ˌfəʊtəʊzɪŋˈkɡrəfɪ| — A form of photolithography using a zinc plate
phrase |freɪz| — an expression consisting of one or more words forming a grammatical constituent of a sentence
phrase-book |ˈfreɪz bʊk| — A (usually pocket-sized) book consisting of everyday expressions and vocabulary in two languages and intended for travellers who wish to communicate with locals while in other countries (regions in which a different language is spoken).
phrasemonger — (derogatory) One who uses overelaborate or wordy phrases.
phraseological |ˌfreɪziːəˈlɑːdʒɪkəl| — Of or pertaining to phraseology.
phraseology |ˌfreɪzɪˈɑːlədʒɪ| — the manner in which something is expressed in words
phrasing |ˈfreɪzɪŋ| — the grouping of musical phrases in a melodic line
phratry |ˈfreɪtrɪ| — people descended from a common ancestor
phrenetic |frəˈnetɪk| — excessively agitated; distraught with fear or other violent emotion
phrenic |ˈfrenɪk| — of or relating to the diaphragm
phrenological |ˌfrenəˈlɒdʒɪkəl| — of or relating to phrenology
phrenologist |frɪˈnɒlədʒɪst| — someone who claims to be able to read your character from the shape of your skull
phrenology |frəˈnɑːlədʒɪ| — a now abandoned study of the shape of skull as indicative of the strengths of different faculties
Phrygian |ˈfrɪdʒɪən| — a native or inhabitant of Phrygia
phthisic |ˈθaɪsɪk| — (pathology) A wasting illness of the lungs, such as asthma or tuberculosis; phthisis.
phthisical |ˈtɪzɪkəl| — phthisic
phthisis |ˈθaɪsɪs| — involving the lungs with progressive wasting of the body
phut |ˈfət| — A sound resembling the release of a blast of steam or exhaust.
phyla |ˈfaɪlə| — plural form of phylum
phylactery |fəˈlæktʌriː| — (Judaism) either of two small leather cases containing texts from the Hebrew Scriptures (known collectively as tefillin); traditionally worn (on the forehead and the left arm) by Jewish men during morning prayer
phyllophagous |fɪˈlɑːfəɡəs| — (zoology) Subsisting on leaves; leaf-eating.
phylloxera |ˌfɪləkˈsiːrə| — type genus of the Phylloxeridae: plant lice
phylogenesis |faɪləʊˈdʒenəsɪs| — (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms
phylogenetic — of or relating to the evolutionary development of organisms
phylogeny |faɪˈlɑːdʒənɪ| — (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms
phylum |ˈfaɪləm| — (linguistics) a large group of languages that are historically related
physic |ˈfɪzɪk| — a purging medicine; stimulates evacuation of the bowels
physical |ˈfɪzɪkl| — having substance or material existence; perceptible to the senses
physicality |ˌfɪzɪˈkælətɪ| — preoccupation with satisfaction of physical drives and appetites
physically |ˈfɪzɪklɪ| — in accord with physical laws
physician |fɪˈzɪʃn| — a licensed medical practitioner
physicist |ˈfɪzɪsɪst| — a scientist trained in physics
physics |ˈfɪzɪks| — the science of matter and energy and their interactions
physiocrat |ˈfɪzɪəkræt| — (economics, historical) Any of a group of economists in 18th century France who believed that the government should not seek to influence the operation of natural economic laws.
physiognomic |ˌfɪzɪəˈnɒmɪk| — Of or pertaining to physiognomy
physiognomical — Of or pertaining to physiognomy.
physiognomist |ˌfɪzɪˈɒnəmɪst| — One who studies, or is an expert in, physiognomy; one who studies the outer appearance of the person (primarily the face) to acquire knowledge of the inner personality.
physiognomy |ˌfɪzɪˈɑːnəmɪ| — the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)
physiographer |ˌfɪzɪˈɒɡrəfə| — A specialist in physiography.
physiographic |ˌfɪzɪəˈɡræfɪk| — Of or pertaining to physiography
physiography |fɪziːˈɑːɡrəfiː| — the study of physical features of the earth's surface
physiologic |ˌfɪzɪəˈlɒdʒɪk| — of or consistent with an organism's normal functioning
physiological |ˌfɪzɪəˈlɑːdʒɪkəl| — of or consistent with an organism's normal functioning
physiologically |ˌfɪzɪəˈlɑːdʒɪklɪ| — of or relating to physiological processes; with respect to physiology
physiologist |ˌfɪzɪˈɑːlədʒəst| — a biologist specializing in physiology
physiology |ˌfɪzɪˈɑːlədʒɪ| — the branch of the biological sciences dealing with the functioning of organisms
physiotherapy |ˌfɪzɪəʊˈθerəpɪ| — therapy that uses physical agents: exercise and massage and other modalities
physique |fɪˈziːk| — constitution of the human body
phytogenesis — (biology) The origin and evolutionary development of plants.
phytogeny |faɪˈtɒdʒɪnɪ| — (biology) phytogenesis
phytology — the branch of biology that studies plants
phytophagous |faɪˈtɑːfəɡəs| — (of animals) feeding on plants
phytoplankton |ˈfæɪtəʊˌplæŋ(k)t(ə)n| — photosynthetic or plant constituent of plankton; mainly unicellular algae