How?

So, how do you tell complete strangers who are clueless with the adoption world, that I really would rather them NOT refer to our Birth Mother as, 'their Mother'?

I know they mean know harm when asking questions, and do not realize what they are saying and how it can hurt my feelings (and maybe even the feelings of MY children when they are older). But it still stings and I wish people would think first, or just automatically have the knowledge of adoption terms. Which I know is unrealistic. But I can wish.