full stop vs punctuation mark

full stop and punctuation mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
full stop	Yes	No	No	No
punctuation mark	Yes	No	No	No

As nouns, punctuation mark is a hypernym of full stop; that is, punctuation mark is a word with a broader meaning than full stop:

full stop: a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations
punctuation mark: the marks used to clarify meaning by indicating separation of words into sentences and clauses and phrases

Other hypernyms of full stop include punctuation.

full stop (noun)	punctuation mark (noun)
a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations	the marks used to clarify meaning by indicating separation of words into sentences and clauses and phrases