Uses of shall and will

With first person pronouns
With first person pronouns shall simply expresses the strong possibility or near certainty of an action or event which is to take place in the future.

• We shall leave for Mumbai tomorrow.
• I shall invite them to dinner.

With second and third person pronouns
When used with second and third person pronouns shall may express a command.

• You shall not steal.
• He shall obey my instructions.
• You shall go at once.

Shall is sometimes used to make a promise.

• You shall be given a present if you stand first in the exam.

Shall can also be used to express a threat.

• He shall regret this.
• You shall be dismissed from service.

Uses of Will
When used with first person pronouns will expresses determination on the part of the speaker. It may also express ideas such as promise, threat or willingness.
Determination

• I will go whatever happens.
• We will not wait any longer.

Promise

• I will try to get you a good job.

Threat

• I will teach you a lesson.
• We will punish any one who creates trouble.

Willingness
Will may also express willingness.

• ‘There is the door bell.’ ‘I will go.’
• ‘He is taking a bath at the moment’. ‘OK, I will wait.’

With second and third person pronouns
When used with second and third person pronouns, will expresses simple futurity.

• The train will leave at 6 am.
• He will be back in an hour.

Notes
Will and shall are followed by an infinitive without to.

• I will wait. (NOT I will to wait.)

There is no -s in the third person singular.

• He will wait. (NOT He will waits.)

Questions and negatives are made without do.

• He will come.
• Will he come?
• He will not come.

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