father vs father-in-law

father and father-in-law both are nouns.

Word	Noun	Adjective	Verb	Adverb
father	Yes	No	Yes	No
father-in-law	Yes	No	No	No

As nouns, father-in-law is a hyponym of father; that is, father-in-law is a word with a more specific, narrower meaning than father:

Other hyponyms of father include dad, dada, daddy, pa, papa, pappa, pop, old man, pater.

father (noun)	father-in-law (noun)
a male parent (also used as a term of address to your father)	the father of your spouse
the founder of a family
a person who holds an important or distinguished position in some organization
a person who founds or establishes some institution
the head of an organized crime family

father (verb)	father-in-law (verb)
make (offspring) by reproduction