Cases of word usage

1) a cereal plant and its seed (called grain) used for food and for making beer and whiskey (barley)

2) the body or frame of the ship; the outer covering of some cereal plants and seeds, especially the pods of peas and beans (hull)

3) grain from a cereal plant used as food (oats for horses, oatmeal for people) (oats)

4) a group of cereal plants tied together; a group (of arrows etc) tied together (sheaf)