Inessential means not needed. Details can be inessential; a tool, a rule, or a step can be inessential if the main thing still works without it. It is also used as a noun for one such thing: an inessential. The word is a little formal. In daily talk people say you don't need it, or it's not necessary. Though actually, what counts as inessential depends on who is speaking: a parent, a boss, or a student may cut very different things and still call them inessential. Opposite of essential — and essential here means needed, not 'the oil' or 'the basic nature of a thing,' though that older sense of essence sits underneath.