• Modal Auxiliary Verbs - Shall Definition

  The modal auxiliary verb shall is used in many of the same ways as will: to form future tenses, to make requests or offers, to complete conditional sentences, or to issue maxims or
  commands. Although will is generally preferred in modern English (especially American English), using shall adds an additional degree of politeness or formality to the sentence that will sometimes lacks.
  Generally, shall is only used when I or we is the subject, though this is not a strict rule (and does not apply at all when issuing commands, as we’ll see).

  Creating the future tense

  The future tenses are most often formed using will or be going to.
  We can also use shall to add formality or politeness to these constructions, especially the

  future simple tense and the future continuous tense. For example:

• “I shall call from the airport.” (future simple tense)
• “We shall be staying in private accommodation.”
• “Our company shall not be held accountable for this.”
• “I shan’t* be participating in these discussions.”
  (*Contracting shall and not into shan’t, while not incorrect, sounds overly formal and stuffy in modern speech and writing; for the most part, it is not used anymore.)
  It is also possible, though far less common, to use shall in the future perfect and future perfect continuous tenses as well:
• “As of next week, I shall have worked here for 50 years.”
• “By the time the opera begins, we shall have been waiting for over an hour.”

  Offers, suggestions, and advice

  When we create interrogative sentences using shall and without question words, it is usually to make polite offers, invitations, or suggestions, as in:
• “Shall we walk along the beach?”
• “Shall I wash the dishes?”
  When we form an interrogative sentence with a question word (who, what, where, when, or how), shall is used to politely seek the advice or opinion of the listener about a future decision, as in:
• “What shall I do with this spare part?”
• “Where shall we begin?”
• “Who shall I invite to the meal?”

  Conditional sentences

  Like will, we can use shall in conditional sentences using if to express a likely hypothetical outcome. This is known as the first conditional. For example:
• “If my flight is delayed, I shall not have time to make my connection.”
• “I shall contact the post office if my package has not arrived by tomorrow.”

  Formal commands

  While will is often used to form commands, we use shall when issuing more formal directives or maxims, as might be seen in public notices or in a formal situation, or to express a reprimand in a formal way. When used in this way, shall no longer has to be used solely with I or we as the subject. For example:
• “This establishment shall not be held liable for lost or stolen property.”
• “Students shall remain silent throughout the exam.”
• “The new law dictates that no citizen shall be out on the streets after 11 PM.”
• “You shall cease this foolishness at once!”

  Substituting Modal Verbs

  In many cases, modal auxiliary verbs can be used in place of others to create slightly different meanings. For example, we can use the word should in place of shall when issuing a command that is not mandatory, but rather is a guideline or recommendation. If, however, we want to express that the command or maxim is an absolute requirement, we can use must instead of shall in this context.
  Explore the section Substituting Modal Verbs to see how and when other modal auxiliary
  verbs overlap.