shall and should

Shall, should, will, would, can, could, may, might and must are modal verbs. They are used to express meaning of certainty or obligation and freedom to act.



Subject + modal + base form of second verb
shall Shall is normally used in British English with the 1st person singular (I shall) and plural (we shall). Will (not shall) is normally used in American English.
certainty We shall go on a holiday next week.
decisions & desires I shall give up smoking.
formal rules & regulations All teachers shall submit their monthly progress reports.
questions Where shall we go? asking for a decision, an opinion or instructions
Shall we go to the cinema? making an offer or suggestion
should advice People with high cholesterol should eat food low in saturated fats.
obligation Everyone should cover his or her mouth and nose with a tissue or handkerchief when coughing or sneezing.
logical probability He should be home by now since he left an hour ago.
reported speech "Shall I carry your bag?"

He wants to know if he should carry your bag.