open interval vs unbounded interval

open interval and unbounded interval both are nouns.

Word	Noun	Adjective	Verb	Adverb
open interval	Yes	No	No	No
unbounded interval	Yes	No	No	No

As nouns, open interval and unbounded interval are synonyms defined as:

open interval and unbounded interval: an interval that does not include its endpoints

open interval (noun)	unbounded interval (noun)
an interval that does not include its endpoints	an interval that does not include its endpoints