is a specific kind of: cereal, food grain, grain.

is a broader term that covers: pearl barley.

is a part of: common barley, Hordeum vulgare.

is a specific kind of: cereal, cereal grass.

is a broader term that covers: common barley, Hordeum vulgare | barley grass, Hordeum murinum, wall barley | foxtail barley, Hordeum jubatum, squirreltail barley, squirreltail grass | Hordeum pusillum, little barley.

is a member of: genus Hordeum, Hordeum.