Definition of "grain"

grain¹

/ɡɹeɪn/

noun
countable and uncountable, plural grains
1. (uncountable) The harvested seeds of various grass food crops eg: wheat, corn, barley.
2. (uncountable) Similar seeds from any food crop, e.g., buckwheat, amaranth, quinoa.
3. (countable) A single seed of grass food crops.
4. (countable, uncountable) The crops from which grain is harvested.
5. (uncountable) A linear texture of a material or surface.
6. (countable) A single particle of a substance.
7. (countable) Any of various small units of mass originally notionally based on grain's weight, variously standardized at different places and times, including
  1. The English grain of 1⁄5760 troy pound or 1⁄7000 pound avoirdupois, now exactly 64.79891 mg.
  2. The metric, carat, or pearl grain of 1⁄4 carat used for measuring precious stones and pearls, now exactly 50 mg.
  3. (historical) The French grain of 1⁄9216 livre, equivalent to 53.11 mg at metricization and equal to exactly 54.25 mg from 1812–1839 as part of the mesures usuelles.
8. (countable, chiefly historical) Any of various small units of length originally notionally based on a grain's width, variously standardized at different places and times.
9. (countable, historical) The carat grain of 1⁄4 carat as a measure of gold purity, creating a 96-point scale between 0% and 100% purity.
10. (materials) A region within a material having a single crystal structure or direction.
11. (astronautics) The solid piece of fuel in an individual solid-fuel rocket engine.
12. A reddish dye made from the coccus insect, or kermes; hence, a red color of any tint or hue, as crimson, scarlet, etc.; sometimes used by the poets as equivalent to Tyrian purple.
  Quotations
  all in a robe of darkest grain
  1646 (indicated as 1645), John Milton, “Penseroso”, in Poems of Mr. John Milton, […], London: […] Ruth Raworth for Humphrey Mosely, […]
  […] doing as the dyers do, who, having first dipped their silks in colours of less value, then give them the last tincture of crimson in grain.
  a. 1825, Quoted by Coleridge, preface to Aids to Reflection
13. The hair side of a piece of leather, or the marking on that side.
  Quotations
  The grain of the leather is also sometimes damaged by the filling , by the taking off the hair , and by the river work.
  1773, Royal Dublin Society, The Art of Tanning and of Currying Leather
14. (in the plural) The remains of grain, etc., after brewing or distillation; hence, any residuum.
15. (botany) A rounded prominence on the back of a sepal, as in the common dock.
16. Temper; natural disposition; inclination.
  Quotations
  brothers […] not united in grain
  a. 1628 (date written), John Hayward, The Life, and Raigne of King Edward the Sixt, London: […] [Eliot’s Court Press, and J. Lichfield at Oxford?] for Iohn Partridge, […], published 1630
17. (photography, videography) Visual texture in processed photographic film due to the presence of small particles of a metallic silver, or dye clouds, developed from silver halide that have received enough photons.
verb
third-person singular simple present grains, present participle graining, simple past and past participle grained
1. To feed grain to.
2. (transitive) To make granular; to form into grains.
3. (intransitive) To form grains, or to assume a granular form, as the result of crystallization; to granulate.
4. To texture a surface in imitation of the grain of a substance such as wood.
5. (tanning) To remove the hair or fat from a skin.
6. (tanning) To soften leather.
7. To yield fruit.

grain²

/ɡɹeɪn/

noun
plural grains
1. A branch of a tree; a stalk or stem of a plant.
2. A tine, prong, or fork.
  1. One of the branches of a valley or river.
  2. An iron fish spear or harpoon, with a number of points half-barbed inwardly.
    Quotations
    Served 5 lb of fish per man which was caught by striking with grains
    4 May 1770, Stephen Forwood (gunner on H.M. Bark Endeavour), journal (quoted by Parkin (page 195)
  3. A blade of a sword, knife, etc.
3. (founding) A thin piece of metal, used in a mould to steady a core.