Key difference: ‘Will’ is used to imply volition or intention, while ‘shall’ can imply necessity or implication.

Both, will and shall are types of modal verbs in the English language. Modal verbs are a small class of auxiliary verbs used mostly to express modality. Modality is basically a possibility or an obligation. Other modal verbs include can, could, may, must, should, would and might.

According to Dictionary.com, the term ‘will’ is described as:

• Am (is, are, etc.) about or going to: I will be there tomorrow. She will see you at dinner.
• Am (is, are, etc.) disposed or willing to: People will do right.
• Am (is, are, etc.) expected or required to: You will report to the principal at once.
• May be expected or supposed to: You will not have forgotten him. This will be right.
• Am (is, are, etc.) determined or sure to (used emphatically): You would do it. People will talk.
• Am (is, are, etc.) accustomed to, or do usually or often: You will often see her sitting there. He would write for hours at a time.
• Am (is, are, etc.) habitually disposed or inclined to: Boys will be boys. After dinner they would read aloud.
• Am (is, are, etc.) capable of; can: This tree will live without water for three months.
• Am (is, are, etc.) going to: I will bid you “Good night.”

Dictionary.com describes ‘shall’ as:

• Plan to, intend to, or expect to: I shall go later.
• Will have to, is determined to, or definitely will: You shall do it. He shall do it.
• (In laws, directives, etc.) must; is or are obliged to: The meetings of the council shall be public.
• (Used interrogatively in questions, often in invitations): Shall we go?

Essentially, ‘will’ and ‘shall’ are both used for the same purpose. They can be used to express future plans interchangeably, especially in British English. However, ‘shall’ is rarely used in contemporary American English.

Currently, ‘will’ is the international standard choice for expressing future plans and expectations, while ‘shall’ is often used in the first-person context to express politeness.  ‘Shall’ is also mainly used in third-person context in legal statements for stating requirements. ‘Will’ can also be used to imply volition or intention, while ‘shall’ can imply necessity or implication.

Further examples of ‘will’:

• I will scale Mount Everest.
• I will call you later.
• I will grow old some day.
• Will they be here tomorrow?
• Will we get tea here?
• I will see you tomorrow.
• Will you marry me?
• I will have my way.
• Will you come with me?
• Boys will be boys.
• A coat will last two years with care.
• You will still be talking.
• The new generator will be used to power the operations tent.

Further examples of ‘shall’:

• You shall take the garbage out before you do anything else.
• I shall visit him later.
• Shall we dance?
• I shall grow old some day.
• We shall all grow old some day.
• Shall we have a cup of tea?
• You shall regret it before long. (My threat)
• You shall not pass! (My command)
• You shall go to the ball. (My promise)
• The prize is to be given to whoever shall have done the best.
• The selected generator shall provide a minimum of 80 Kilowatt-hours.

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