emoticon vs smiley

emoticon and smiley both are nouns.

Word	Noun	Adjective	Verb	Adverb
emoticon	Yes	No	No	No
smiley	Yes	No	No	No

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

emoticon: a representation of a facial expression (as a smile or frown) created by typing a sequence of characters in sending email
smiley: an emoticon of a smiling face

emoticon (noun)	smiley (noun)
a representation of a facial expression (as a smile or frown) created by typing a sequence of characters in sending email	an emoticon of a smiling face