Photosynthesis is the process of green plants manufacturing their food with the use of water , carbon dioxide in the presence of light giving out oxygen as the by product 
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This is the process by which green plants manufacture their food (organic compounds) from carbon(4) oxide and water in the presence of sunlight energy absorbed by chlorophyll, releasing oxygen as a by product.
the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.