Is there any difference between allude and refer? And if so, what?

The answer to the first question is—it depends. Depends on the user, for one thing. To many people, the words mean essentially the same, and can be used interchangeably. But to others—including most careful (and most-careful) writers and speakers, there’s a distinct and significant difference.

These people are much more likely to use the term allude in a special sense—as when making an indirect reference. So if someone were to say “Chris, the editor, will probably object to the article,” that person would be referring to a specific, identified editor. But in the sentence “Be careful, you-know-who in the upstairs office won’t like that,” the writer is making an allusion—an indirect reference.

And the answer also depends on the reference or authority we depend on (refer to?). Webster’s New World Dictionary lists refer as a synonym for allude. But the definition given in the same book is “to refer in a casual or indirect way.”

One of my usage dictionaries has three small-print pages on the arguments over refer and allude, including many quotes from well known writers and speakers. The examples make it clear that whichever side you come down on, you’ll have lots of support for your choice.

We recommend using refer when the object (referent) is clear (as when named), and allude when the referent is intentionally or unintentionally left unnamed.

Final note: the term allude comes from Latin alludere, to joke or jest. It’s related to ludicrous, which some people might use in referring or alluding to this whole word-choice argument.