Other forms: grains
Grain is the pattern of lines running through wood, showing which way the fibres lie. Run a thumb along a pine shelf and you can feel it; sand across those lines instead of along them and the surface goes rough.
The same word covers the seed of cereal plants — wheat, oats, rice — and the crop in bulk: a ship carrying grain, a barn full of it. A grain is also one tiny hard piece of anything: a grain of sand, a grain of rice, a few grains of sugar left in the bowl. In photography and film, grain is the speckled texture you see in old prints and in shots taken in poor light. Something that goes against the grain is uncomfortable to do because it runs against your nature, and you take a story with a grain of salt when you only half believe it. In the wood sense it stays uncountable: the grain of the oak, never the grains.
1noungrainThe pattern and direction of the fibres in wood, stone or fabric.
“Paint along the grain, not across it, or the brush marks will show.”
2nounseedsThe seeds of cereal plants such as wheat, rice and oats, grown as a crop or eaten as food.
“The lorries were loaded with grain for the port.”
3nounsingleA single tiny hard piece of something.
“A grain of sand had worked its way into the watch.”
4nounspeckledThe speckled texture visible in a photograph or film image.
“The photograph has a heavy grain that suits the black and white.”
grain is a pattern in wood.
Grain came through Old French from Latin grānum, seed, and behind that the Indo-European *ǵr̥h₂nóm. English collected the same ancient word more than once: corn and gram are its doublets, the same seed arriving by different roads. So the wheat in the barn, the sand on the beach and the lines in a plank are all named after one small hard seed.
Proto-Indo-European
*ǵerh₂-
Proto-Indo-European
*ǵr̥h₂nóm — grain
Latin
grānum — seed
Old French
grain
Middle English
greyn
English, today
grain
From Middle English greyn, grayn, grein, from Old French grain, grein, from Latin grānum (“seed”), from Proto-Indo-European ǵr̥h₂nóm (“grain”). a doublet of corn and gram and granum and grao.
Etymology from Wiktionary, CC BY-SA