allow, permit and let

allow and permit

These words have similar meanings and uses. Permit is more formal. Both words can be followed by object + infinitive.

• We do not allow/permit people to smoke in the kitchen.

When there is no personal object, an -ing form is used.

• We do not allow/permit smoking in the kitchen.

Passive structures are common; personal subjects and gerund (-ing form) subjects are both possible.

• People are not allowed/permitted to smoke in the kitchen.
• Smoking is not allowed/permitted in the kitchen.

The passive structure with it is only possible with permit.

• It is not permitted to smoke in the kitchen. (but not It is not allowed to smoke …)

Allow, but not permit, can be used with adverb particles.

• She wouldn’t allow me in.
• Emily isn’t allowed out at night.

let

Let is the least formal of these three words, and is followed by object + infinitive without to. Compare:

• Please allow me to buy you a drink. (polite and formal)
• Let me buy you a drink. (friendly and informal)

Let is not usually used in the passive.

• I wasn’t allowed to pay for the drinks. (not I wasn’t let …)

Let can be used with adverb particles; passives are possible in this case.

• She wouldn’t let me in.
• I’ve been let down.

note

For more about let, (see here), (see here).