Grammar Point
expressions (phrases, clauses, etc.)
exp 
polite (teineigo) language
pol 
ましょう

I'll

used to express volition; ましょ is col.; まひょ is ksb

let's

used to make an invitation, request, etc.

Verb ます stem + ましょう

ましょう is a formal verb ending used to express the speaker's volition or to invite someone to do something together. It is the polite equivalent of the informal volitional form (Verb ます stem + よう).

Volition (I will)

Used when the speaker declares their own intention to do something in a polite manner.

I will write a letter.

I will buy a book.

Invitation (Let's)

Used when the speaker is inviting the listener to do an activity together.

Let's eat lunch.

Let's go to the park.

Note

In casual speech, ましょ is sometimes used. In the Kansai dialect, まひょ is used instead. When used as an invitation, it often translates to 'Let's', and when used to express the speaker's own will or offer to do something, it translates to 'I will' or 'I shall'.

Words: 
ましょう
ましょ
まひょ
Radicals of radicals