Immaterial
Part of speech: adjective
Definition: Having no matter or substance. Irrelevant.
Example sentence: Genre is a useful thing when organizing texts in a bookshop but immaterial to the particular exchange between writer and reader.
Unimportant
Part of speech: adjective
Definition: petty; not important or noteworthy
Example sentence: Failure is unimportant. It takes courage to make a fool of yourself.