I believe the easiest way to differentiate them is to use <acronym> if you can speak it like a word, not spell them out like a group of letters. We say “ray-dar”, not are-aay-dee-ayy-are. So we get <acronym title=”Radio Detection and Ranging”>Radar</acronym>. If spelling them out letter by letter it’s an <abbr>, like this <abbr [...]
