How do you say devil in Gaelic?

There isn't one single word for "devil" in Gaelic that covers all the nuances of the English word. The best translation depends on the context and which specific aspect of "devil" you want to convey. Here are a few options, each with slightly different connotations:

* Diafol: This is probably the closest single-word translation and is derived from the Latin "diabolus." It's a common and widely understood term.

* Deimhin: This word translates more to "demon" or "evil spirit," and might be a better fit if you're talking about a specific evil entity rather than the Devil as a figurehead of evil.

* An Diabhal: This is simply "The Devil," a more formal and definite term.

The best choice depends heavily on context. For general use, Diafol is a good starting point.