These words refer to whatever is not an inherent part of a given consideration or entity. Extraneous stress something that is not necessary or has no bearing, but the word is otherwise very general in its implications. It does suggest a difference in kind: sorting out the hard-core facts from the extraneous interpretation. The unnecessary element referred to may, if not excluded, her either harmless or deleterious: extraneous substances that make the sunburn preparation smell pleasant but have no healing effect; extraneous minerals in the water supply that made it unsafe to drink. Superfluous is different in its effect, often pointing to simple excess, not a difference in kind: wiping away the superfluous oil with a lean rag. Even where the word shows a less clear-cut contrast with extraneous, it still points to what is useless or redundant: a room cluttered with superfluous furniture.

By contrast, extrinsic functions as an intensification of extraneous , emphasizing that something is by its very nature completely unlike a given entity or completely outside the scope of some concern: pointing out that oxygen consumption might well be extrinsic to the life cycle as it may have developed in other parts of the universe; literary standards that are extrinsic to any understanding of popular media. Inessential is more like extraneous in referring to what may be present and tolerated but is in any case not needed and may therefore be excluded by choice or necessity: an editor who helped the novelist cut from his book those scenes that were inessential to the main theme; ordering the people in the lifeboat to throw overboard everything that was inessential to their survival.

Immaterial refers not to what is unnecessary, in excess or unlike something else, but to what has no effect or makes no difference: She told him that it was immaterial to her whether he stayed or left. In the context of reasoning, the word may point to what contributes nothing to an objective proof and thus is unimportant: the judge’s ruling that the political beliefs of the accused were immaterial to the question of his guilt. Irrelevant also indicates what is unimportant or inapplicable, in this case because it lacks any direct bearing on the concern at hand: proof that the mother’s dreams were irrelevant to the development of the foetus. Most specifically, the word suggests a lack of logical relationship as in a non sequitur: injecting irrelevant details about the man’s life into our consideration of his candidacy.