Which word is synonymous with 'not needed'?

The word 'unnecessary' is synonymous with 'not needed' because it directly conveys the idea that something is superfluous or not required in a particular context. When we say that something is unnecessary, we indicate that it does not serve a purpose or is excessive.

In contrast, other options like 'essential,' 'required,' and 'obligatory' all imply a sense of need or obligation. These words suggest that something is important or mandatory, which is the opposite of being 'not needed.' Therefore, 'unnecessary' accurately captures the concept of lacking necessity.