grain has 7 distinct synonyms spread across 7 of its 15 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
foodstuff prepared from the starchy grains of cereal grasses
Synonyms, antonyms and the broader and narrower relations for grain come from Princeton University’s WordNet. Full sources and licences.
the side of leather from which the hair has been removed
a weight unit used for pearls or diamonds: 50 mg or 1/4 carat
1/60 dram; equals an avoirdupois grain or 64.799 milligrams
1/7000 pound; equals a troy grain or 64.799 milligrams
a cereal grass
“wheat is a grain that is grown in Kansas”
the smallest possible unit of anything
“there was a grain of truth in what he said”
the direction, texture, or pattern of fibers found in wood or leather or stone or in a woven fabric
“saw the board across the grain”
the physical composition of something (especially with respect to the size and shape of the small constituents of a substance)
“breadfruit has the same texture as bread”
paint (a surface) to make it look like stone or wood