Should vs Shall vs Must?

API 682 4th Edition uses the word “should” a total of 183 times! “Shall” is used 822 times. When an API standard says you shall do something, it means that you are required to do so. ... In fact, “must” is the only word that imposes a legal obligation that something is mandatory.

What is the difference between shall and should?

'Should' is used in informal writing mainly, and as the past tense of 'Shall'. 'Shall' is used to express ideas and laws. 'Should' is used to express personal opinions and desires, and primarily to give advice. 'Shall' can be used when a speaker wishes to convey something that will take place in the future.

Should vs shall legally?

The word should does not express a legal requirement. But shall, in the case of the climate agreement, does. Shall we continue? We often use the auxiliary verb shall to indicate a promise.