A forget-me-not is a small plant. The flowers are usually a pale, clear blue, with a tiny yellow or white eye in the middle; pink and white ones exist too. They are low, with many little blooms, and people plant them in spring gardens. The English name is not an ordinary noun built like teacher or baker. It is a tiny sentence — “do not forget me” — copied piece by piece from an older French name (ne m'oubliez mie) or the German name Vergissmeinnicht. That is why it is written with hyphens. The old idea is that you give someone the flower so they will remember you; in ordinary talk now it is almost always just the plant, though people sometimes use the name, half-joking, for a small gift that says “think of me.” It is not a verb. You do not “forget-me-not” someone.