How do you say vanity in Gaelic?

There isn't a single perfect translation for "vanity" in Gaelic, as the meaning can be nuanced. The best choice depends on the specific shade of meaning you intend:

* For the sense of excessive pride in one's appearance: You might use phrases that emphasize pride or self-importance, such as `uaill` (pride) or `bród` (pride, boastfulness) in conjunction with words describing appearance. For example, you could say something like "uaill ró-mhór ina chuma" (excessive pride in his/her appearance). This is descriptive rather than a direct translation.

* For the sense of emptiness or worthlessness of worldly things: This aspect might be better captured using words related to `díomhaoineas` (futility) or `éagóir` (vanity as in the fleeting nature of things).

* For vanity in the sense of a bathroom vanity: This would require a descriptive phrase, for example, "cófra folctha" (bathroom cabinet) or something similar depending on the style.

In short, there's no single word equivalent. You need to choose the most appropriate words or phrase to convey the intended meaning of "vanity" within the context of your sentence.