How can I make sure that my iphone can never type a certain word?

When I want to type the word "and" in a conversation, somehow I will accidentally type exactly this word instead "a 's" (without parenthesis of course) and I have no idea how I am doing it, but I do it consistently. It literally puts it like that ----> a 's. I would guess I just need to slow down and type better but I would love to make it so that my phone can never, ever, EVER type a 's again as long as I live. Everything I have tried doesn't work. Any help would be greatly appreciated. The word is the letter a followed by a single space and then the 's. Like that ----> a 's