From BiblePortal Wikipedia

King James Dictionary [1]

Grain n. L. granum.

1. Any small hard mass as a grain of sand or gravel. Hence, 2. A single seed or hard seed of a plant, particularly of those kinds whose seeds are used for food of man or beast. This is usually inclosed in a proper shell or covered with a husk,and contains the embryo of a new plant. Hence, 3. Grain, without a definitive, signifies corn in general, or the fruit of certain plants which constitutes the chief food of man and beast, as wheat, rye, barley, oats and maiz. 4. A minute particle. 5. A small weight, or the smallest weight ordinarily used, being the twentieth part of the scruple in apothecaries' weight, and the twenty fourth of a pennyweight troy. 6. A component part of stones and metals. 7. The veins or fibers of wood or other fibrous substance whence, cross-grained, and against the grain. 8. The body or substance of wood as modified by the fibers.

Hard box, and linden of a softer grain.

9. The body or substance of a thing considered with respect to the size, form or direction of the constituent particles as stones of a fine grain.

The tooth of a sea-horse,contains a curdled grain.

10. Any thing proverbially small a very small particle or portion as a grain of wit or of common sense.

Neglect not to make use of any grain of grace.

11. Dyed or stained substance.

All in a robe of darkest grain.

12. The direction of the fibers of wood or other fibrous substance hence the phrase, against the grain, applied to animals, that is, against their natural tempers. 13. The heart or temper as brothers not united in grain. 14. The form of the surface of any thing with respect to smoothness or roughness state of the grit of any body composed of grains as sandstone of a fine grain. 15. A tine, prong or spike.

A grain of allowance, a small allowance or indulgence a small portion to be remitted something above or below just weight.

To dye in grain, is to dye in the raw material, as wool or silk before it is manufactured.

GRAIN, To yield fruit.

GRAIN, or GRANE, for groan. Not in use.

Vine's Expository Dictionary of NT Words [2]

1: Κόκκος (Strong'S #2848 — Noun Masculine — kokkos — kok'-kos )

denotes "a grain,"  Matthew 13:31;  17:20;  Mark 4:31;  Luke 13:19;  17:6;  John 12:24 (AV, "corn");   1—Corinthians 15:37 (where the RV has "a ... grain," to distinguish it from "grain" in general). See Corn.

Holman Bible Dictionary [3]

 Genesis 30:14 Exodus 9:32 Exodus 9:31 Ezekiel 4:9

Easton's Bible Dictionary [4]

 Amos 9:9 Matthew 13:31 John 15:37

American Tract Society Bible Dictionary [5]

See Corn .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [6]

(occurs only as a rendering of צְרוֹר , a small Stone or kernel,  Amos 9:9; Κόκκος , a beasry or individual seed, e.g. of mustard,  Matthew 13:31, etc.; or wheat,  John 12:24;  1 Corinthians 15:37) is snot used in the A.V. in our American collective sense of corn (q.v.) in general, which is the signification of דָּגָן , בִּר , or שֶׁבֶר . Thea Hebrews planted only wheat, bcaley, and spelt (comp.  Isaiah 28:25;  Ezekiel 4:9); rye and oats are not mentioned in the Bible (in the Talmud five species of grain are named, Mishna, Naedr. 7:2; and some find even rye and oats in the שבלת שׁו ל והשוכין 10:7). On the other band, some (e.g. Michaelis) think that rice is referred to by שׂוֹרָה ( Isaiah 28:25), in opposition to Rosenmuller and Gesenius. As diseases of seed-grain, יֵרָקוֹן , Paleness ("mildew"), and

שַׁדָּפוֹן , Blight ("blasting"), are mentioned. (See Cereals).