must

 "Must" is a word that signifies a strong requirement or obligation. For example, "You must wear a seatbelt while driving" emphasizes the necessity of wearing a seatbelt for safety. It can also express a logical inference, such as "The sun is shining, so it must be a sunny day" indicating a conclusion based on evidence. In both cases, the word "must" conveys a sense of compulsion or certainty.