[hepkatmama]

Q. Like millions of Americans, some cannot grasp the extremely subtle difference between the words ''your'' and ``you're.''

A. Top grammar scientists are often confused by these two words, which are technically known as ''bivalves,'' or words that appear to be identical and have hinged shells. The best way to tell them apart is to remember that ''you're'' is a contraction, which is a type of word used during childbirth, as in: ''Hang on, Marlene, here comes you're baby!'' Whereas ''your'' is, grammatically, a prosthetic infarction, which means a word that is used to score a debating point in an Internet chat room, as in: ``Your a looser, you morron!''