signature vs allograph

signature and allograph both are nouns.

Word	Noun	Adjective	Verb	Adverb
signature	Yes	No	No	No
allograph	Yes	No	No	No

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

signature (noun)	allograph (noun)
a distinguishing style	a variant form of a grapheme, as `m' or `M' or a handwritten version of that grapheme
your name written in your own handwriting	a signature written by one person for another
a sheet with several pages printed on it; it folds to page size and is bound with other signatures to form a book
the sharps or flats that follow the clef and indicate the key
a melody used to identify a performer or a dance band or radio/tv program