question mark vs interrogation point

question mark and interrogation point both are nouns.

Word	Noun	Adjective	Verb	Adverb
question mark	Yes	No	No	No
interrogation point	Yes	No	No	No

As nouns, question mark and interrogation point are synonyms defined as:

question mark and interrogation point: a punctuation mark (?) placed at the end of a sentence to indicate a question

question mark (noun)	interrogation point (noun)
a punctuation mark (?) placed at the end of a sentence to indicate a question	a punctuation mark (?) placed at the end of a sentence to indicate a question