portrait vs portraiture

portrait and portraiture both are nouns.

Word	Noun	Adjective	Verb	Adverb
portrait	Yes	No	No	No
portraiture	Yes	No	No	No

As nouns, portrait and portraiture are synonyms defined as:

portrait and portraiture: a word picture of a person's appearance and character

Other synonyms of portrait include portrayal.

portrait (noun)	portraiture (noun)
any likeness of a person, in any medium	the activity of making portraits
a word picture of a person's appearance and character	a word picture of a person's appearance and character