photosynthesis

noun pho·to·syn·the·sis \ ˌfō-tō-ˈsin(t)-thə-səs \

Updated on: 12 May 2018

Definition of photosynthesis

: synthesis of chemical compounds with the aid of radiant energy and especially light; especially : formation of carbohydrates from carbon dioxide and a source of hydrogen (such as water) in the chlorophyll-containing cells (as of green plants) exposed to light

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photosynthesize

play \ˌfō-tō-ˈsin(t)-thə-ˌsīz\ intransitive verb

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photosynthetic

play \ˌfō-tō-sin-ˈthe-tik\ adjective

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photosynthetically

play \ˌfō-tō-sin-ˈthe-ti-k(ə-)lē\ adverb

See photosynthesis defined for English-language learners

See photosynthesis defined for kids

Recent Examples of photosynthesis from the Web

While walking, the man, a science type who developed ideas for products and companies, described the process of photosynthesis to his fiancee.

— carolyne zinko, San Francisco Chronicle, "A prenup primer: What Silicon Valley couples should consider," 25 Jan. 2018
The consequence is not just outward – zooxanthellae are partners with coral in an ancient symbiotic relationship, conducting photosynthesis necessary for the corals to survive.

— chris mooney, Anchorage Daily News, "Global warming has changed the Great Barrier Reef ‘forever,’ scientists say," 19 Apr. 2018
As the sun angle decreases in the fall, plants lose the light necessary for photosynthesis.

— angela fritz, Washington Post, "Spring is running 20 days early. It’s exactly what we expect, but it’s not good.," 27 Feb. 2018
The spacecraft found high levels of methane and oxygen, suggestions that photosynthesis was occurring on Earth’s surface.

— katherine kornei, Science | AAAS, "Asteroid-bound spacecraft finds signs of life—on Earth," 26 Mar. 2018
Near the surface, invisible to the naked eye, a swarm of microscopic plankton, some orange-pink and others dark green, swim in lazy circles, capturing the sun's rays and using the solar energy to make nutrients through photosynthesis.

— aditee mitra, Scientific American, "Tiny Creatures, Part Plant and Part Animal, May Control the Fate of the Planet," 20 Mar. 2018
Dalba’s contention is that photosynthesis on a planet’s surface, which generates a surfeit of molecular oxygen, is the only thing that can account for these atomic O+ ions in a planet’s ionosphere.

— diana gitig, Ars Technica, "Oxygen ions may be an easy-to-track sign of life on exoplanets," 16 Feb. 2018
More problematic, however, is the fact that life existed on Earth for more than a billion years before photosynthesis filled our skies with oxygen, and similar anaerobic microbes on other planets could happily thrive with no O2 to speak of.

— jay bennett, Popular Mechanics, "The Deep Space Eye in the Desert," 14 Feb. 2018
Six-part series includes topics on: The cell and structure of a plant, mineral nutrition and photosynthesis, respiration and metabolism, Inorganic nutrients and hormones, Plant babies, Cell death, biotic and abiotic stress.

— elaine rewolinski, Milwaukee Journal Sentinel, "Home and Garden events Jan. 14," 11 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'photosynthesis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

photosynthesis Has Greek Roots

The Greek roots of photosynthesis combine to produce the basic meaning "to put together with the help of light". Photosynthesis is what first produced oxygen in the atmosphere billions of years ago, and it's still what keeps it there. Sunlight splits the water molecules (made of hydrogen and oxygen) held in a plant's leaves and releases the oxygen in them into the air. The leftover hydrogen combines with carbon dioxide to produce carbohydrates, which the plant uses as food—as do any animals or humans who might eat the plant.

Origin and Etymology of photosynthesis

New Latin

NEW! Time Traveler

First Known Use: 1898

in the meaning defined above

See Words from the same year

Other Botany Terms

annual, burgeon, chloroplast, nomenclature, succulent, sylvan, xylem

PHOTOSYNTHESIS Defined for English Language Learners

photosynthesis

noun

Definition of photosynthesis for English Language Learners

biology : the process by which a green plant turns water and carbon dioxide into food when the plant is exposed to light

PHOTOSYNTHESIS Defined for Kids

photosynthesis

noun pho·to·syn·the·sis \ ˌfō-tə-ˈsin-thə-səs \

Definition of photosynthesis for Students

: the process by which green plants and a few other organisms (as some protists) form carbohydrates from carbon dioxide and water in the presence of light

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photosynthetic

\-sin-ˈthe-tik\ adjective

photosynthetic activity

Medical Dictionary

photosynthesis

noun pho·to·syn·the·sis \ ˌfōt-ō-ˈsin(t)-thə-səs \

medical Definition of photosynthesis

plural photosyntheses

: synthesis of chemical compounds with the aid of light sometimes including the near infrared or near ultraviolet; especially : the formation of carbohydrates from carbon dioxide and a source of hydrogen (as water) in chlorophyll-containing cells (as of green plants) exposed to light involving a photochemical release of oxygen through the decomposition of water followed by various enzymatic synthetic reactions that usually do not require the presence of light

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photosynthesize

play \-ˌsīz\ also British photosynthesise intransitive verb photosynthesized also British photosynthesised; photosynthesizing also British photosynthesising

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