Docosahexaenoic acid: an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, sperm, testicles and retina. It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk or fish oil. DHA's structure is a carboxylic acid (-oic acid) with a 22-carbon chain (docosa- is Greek for 22) and six (hexa-) cis double bonds (-en).

Source: Wikipedia