"Must-" is a word that implies obligation, necessity or compulsion. There are several synonyms for this word that can convey the same meaning such as imperative, mandatory, essential, necessary, compulsory, and inevitable. These words can be used interchangeably depending on the context of the sentence. For instance, the imperative is used as a command, while the mandatory has the power of an authority. Essential represents a crucial element while necessary refers to something required. Compulsory implies mandatory requirements whereas inevitable is an unavoidable future event. Using synonyms helps to add variety to writing and helps avoid repetitive use of words.