"Must" generally refers to things that must be handled, with an imperative tone, which means must. You must come to work tomorrow. And "necessary" means necessary and indispensable. Food is a necessary food for human beings. Toothbrushes and toothpaste are essential daily necessities.

"Must" means that work and things must be done in this way. It is a voluntary verb and is often used with other verbs. You must study hard. "Necessary" refers to the necessary needs of raw materials, articles, uses, etc. It is a verb, which can be used alone or as an attribute. For example, necessity in Necessities is an attribute.

"Xu" and "Xu" have the same sound, but their forms and meanings are different. The original meaning of "Xu" refers to beard, the common meaning refers to "must", and the common adverbs (such as "need, need, need to know, need to take measures"). The original meaning of "need" refers to stopping and waiting in the rain, and the common meaning refers to "need", which is not only used now, but also can only be formed into compound words or fixed phrases to express the usage of verbs (such as "need, necessity, demand and each has his own needs").

Extended data:

Must is an adverb with emphasis and used as an adverbial. "Must" is often confused with "necessity" in application. "Must" and "inevitable" are synonyms, which have certain meanings. The difference is that the former emphasizes necessity, while the latter emphasizes necessity.

Necessary means unnecessary; Not less. Easily confused with necessities.

References:

Baidu Encyclopedia must be Baidu Encyclopedia.