heir vs heir apparent

heir and heir apparent both are nouns.

Word	Noun	Adjective	Verb	Adverb
heir	Yes	No	No	No
heir apparent	Yes	No	No	No

As nouns, heir apparent is a hyponym of heir; that is, heir apparent is a word with a more specific, narrower meaning than heir:

heir: a person who is entitled by law or by the terms of a will to inherit the estate of another
heir apparent: an heir whose right to an inheritance cannot be defeated if that person outlives the ancestor

Other hyponyms of heir include heir-at-law, heiress, inheritress, inheritrix, heir presumptive.

heir (noun)	heir apparent (noun)
a person who is entitled by law or by the terms of a will to inherit the estate of another	an heir whose right to an inheritance cannot be defeated if that person outlives the ancestor
a person who inherits some title or office