Formal:
* Insignificant: This word emphasizes the lack of size, weight, or importance.
* Trivial: This word suggests something unimportant, petty, or commonplace.
* Unimportant: A straightforward and direct way of saying something lacks importance.
* Irrelevant: This word implies that something is not related to the matter at hand.
* Minor: This word suggests something small or of lesser importance.
Informal:
* Unnecessary: This word implies that something is not needed.
* Frivolous: This word suggests something silly or lacking seriousness.
* Meaningless: This word implies a lack of purpose or significance.
* Nonsensical: This word suggests that something is absurd or lacking logic.
* Secondary: This word implies that something is of less importance than something else.
The best word to use depends on the specific context and the desired level of formality.