Use allow in more formal contexts, followed by to + verb (they allowed him to leave early). Use let in more everyday, informal contexts, followed by the bare infinitive, without “to” (they let him leave early).
The Core Difference
“Allow” is the more formal choice and is grammatically followed by an object plus “to” and the base verb: allow someone to enter, photography is not allowed. It is common in rules, policies, and written notices.
“Let” is more casual and everyday, and it is followed directly by the base verb with no “to”: let me help you, let him speak. Using “to” after “let” (let him to speak) is a very common learner mistake.
- formal, + to + verb → allow: they allow visitors to park here
- everyday, + bare verb → let: they let visitors park here
Allow and Let in Context
The rules do not allow visitors to bring pets inside.
Please let me know if you need anything.
Smoking is not allowed in this building.
Her parents let her stay out until midnight.
The airline does not allow passengers to bring large bags, but they let you check them for free.
Common Mistakes
| Incorrect | Correct | Why |
|---|---|---|
| ✗ let him to speak | ✓ let him speak | let takes the bare infinitive, no “to” |
| ✗ allow him speak | ✓ allow him to speak | allow needs “to” before the verb |
| ✗ they don't let smoking here | ✓ they don't allow smoking here | “let” doesn't take a gerund object this way; “allow” fits better with a noun/gerund |
| ✗ the sign says: allow to enter | ✓ the sign says: entry allowed / visitors allowed to enter | needs an object before “to enter” |
| ✗ please allow me help you | ✓ please allow me to help you | “to” is required after “allow + object” |
ALLOW needs TO, just like the words “allow” and “to” being longer, formal words that go together. LET is short and direct, just like the bare verb that follows it — no “to” needed, exactly like “let go”, not “let to go”.
Related Questions
- Allow vs Let — full confusing-words comparison page with additional examples and exercises.
- All Confusing Words — browse all 300+ word-pair guides.
- All Questions — more quick-answer pages.
- Grammar Quiz — test your knowledge of confusing word pairs.
Frequently Asked Questions
What is the main grammatical difference between allow and let?
“Allow” is followed by an object and “to + base verb” (allow her to leave), while “let” is followed by an object and the bare infinitive with no “to” (let her leave). This is the most common mistake learners make with this pair.
Which word is more formal, allow or let?
“Allow” is generally more formal and is standard in rules, signs, policies, and written instructions (“visitors are not allowed to smoke”), while “let” is more casual and typical of everyday spoken English (“let's go”, “let me see”).
Can allowed be used without an object before to?
Yes, in the passive voice: “Smoking is not allowed” or “Visitors are allowed to enter after 9am.” Here the subject of the sentence becomes the person or thing being permitted, and “to” is only needed when a following verb is included.
Is let me know a fixed expression?
Yes — “let me know” is an extremely common fixed phrase meaning “tell me” or “inform me”: “Let me know if you have questions.” It always uses “let”, never “allow”, in this everyday expression.
Can let be used in formal writing at all?
Yes, but less commonly than “allow”. Formal writing tends to prefer “allow” or “permit” for describing rules and permissions, reserving “let” mostly for direct, conversational suggestions such as “let us now consider…”.
Is permit similar to allow and let?
Yes — “permit” is a more formal synonym of “allow”, and like “allow”, it takes “to + verb”: “The licence permits you to drive commercially.” It shares allow's grammar pattern, not let's.
Why do learners often write let him to go?
Because many other languages use a structure equivalent to “to” after their verb for “let”, learners transfer that pattern into English. English is unusual in requiring the bare infinitive specifically after “let”, “make”, and a few similar verbs.
Are there other verbs that behave like let, without to?
Yes — “make” (make him do it, not “make him to do it”) and, in some structures, “help” (help me do it / help me to do it, both acceptable) follow a similar bare-infinitive pattern to “let”.
Can allow be used to mean provide enough of something?
Yes — “allow” can also mean to set aside or provide enough of a resource: “Please allow 30 minutes for the delivery”, “allow extra time for traffic.” This use has nothing to do with permission.
Is this distinction tested in grammar exams?
Yes — the pattern “let + bare infinitive” versus “allow + object + to + verb” is a classic grammar point tested in school and international English exams, because it highlights a learner's control of verb complementation patterns.