The ulna is one of the two bones in your forearm — the part between elbow and wrist. It sits on the little-finger side, opposite your thumb; its partner, the radius, is on the thumb side. An easy way to feel it: rest your arm on a table, palm down, and run your finger along the edge nearest your little finger. That hard line is your ulna. The pointed bump at your elbow is its top end. The plural is usually ulnae (from Latin), though ulnas is also used and is perfectly clear. The adjective is ulnar, which you will meet in 'ulnar nerve' — the nerve that runs past your elbow and gives you that electric shock when you knock your 'funny bone'. This is an anatomy word: doctors, nurses, physiotherapists, biology students. In ordinary talk people just say 'arm bone' or point. But it is a good word for students because it is one of those Latin bone names that stays the same in every language of medicine, so it is a word you can carry into other subjects.