Why wheat is not a shrub?

Answer 1

Because it is an herbaceous non-woody plant. Wheat is actually a domesticated species of grass, just like the green grass that grows in your lawn. Rice and corn are also grasses, as are oats, barley, and rye.

Answer 2

Wheat (the plant) is, as Cycling-rod says, a cereal grain, which is a type of grass grown for its "fruit". It's definitely not a shrub (a small to medium sized woody plant). It's also not an herb in the culinary sense (a plant grown for its aromatic or savory leaves or flowers), though it is a "herbaceous plant" in the botanical sense (a plant with no persistent woody stem above ground).

Answer 3

Wheat is a cereal grain, from which we get flour.