I saw some where: case doesn't matter and some does matter, so which one is correct???

The problem is the word I am targeting has so few variations! That word is "ad", oh, and "banner" too.

Therefore, in the META tag, I repeat over 3 times each one, can't find a way to avoid it.
Any body has key word suggestions for "ad": advertising, advertisement, advert, banner, and what else???