smiler vs human face

smiler and human face both are nouns.

Word	Noun	Adjective	Verb	Adverb
smiler	Yes	No	No	No
human face	Yes	No	No	No

As nouns, human face is a hypernym of smiler; that is, human face is a word with a broader meaning than smiler:

smiler: the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)
human face: the front of the human head from the forehead to the chin and ear to ear

Other hypernyms of smiler include face.

smiler (noun)	human face (noun)
the human face (`kisser' and `smiler' and `mug' are informal terms for `face' and `phiz' is British)	the front of the human head from the forehead to the chin and ear to ear
a person who smiles