Meaning

• A person, group, or state (etc) which is associated with another for a common cause; one united to another by treaty or common purpose; a confederate.

  "the two countries were allies in WWI"

• A person, group, concept (etc) which is associated with another as a helper; a supporter; an auxiliary.

• Anything akin to something else by structure, etc.

• A closely related species, usually within the same family.

  "Gruiformes — cranes and allies"

• A relative; a kinsman.

Meaning

• To unite, or form a connection between, as between families by marriage, or between princes and states by treaty, league, or confederacy.

• To connect or form a relation between by similitude, resemblance, friendship, or love.