That possibly depends on what A and B are. Words? Functions? A(B), or A (B) are possible.

Like Gary says, use a space when you're separating the bracketed word from other words. "This (is) an example." And within the brackets don't use spaces. ie (is) - notice no spaces within. Also, the word "brackets" is fine. I use it all the time, anyway :) It's just a difference in usage between UK and NA English. I interchange "brackets" and "parentheses" in programming scripts, but always use "brackets" when describing those symbols in sentences.

Oh I see. Thank you!

While you're technically correct, I would suggest using the term "parenthesis" for ( and ) instead of "brackets", which most people (programmers at least) think of as [ and ].