shall

Concise Oxford English Dictionary © 2008 Oxford University Press:
shall/ʃəl/

▶modal verb (3rd sing. present shall)

• 1 (in the first person) expressing the future tense.

• 2 expressing a strong assertion or intention.

• 3 expressing an instruction or command.

• 4 used in questions indicating offers or suggestions.

– origin OE sceal, of Gmc origin, from a base meaning ‘owe’.

usage: There are traditional rules as to when to use shall and will. These state that when forming the future tense, shall should be used with I and we (I shall be late), while will should be used with you, he, she, it, and they (he will not be there). However, when expressing determination or a command this rule is reversed: will is used with I and we (I will not tolerate this), and shall is used with you, he, she, it, and they (you shall go to school). In practice, however, these rules are not followed so strictly and the contracted forms (I'll, she'll, etc.) are frequently used instead, especially in spoken and informal contexts.