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. Mary isn’t allowed out at night.
Let is the least formal of these three words, and is followed by
object + infinitive without to.
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.