"Like" is a preposition followed by a noun or pronoun (similar to); "as" is a conjunction followed by a clause with a verb (in the role of, just as).
Preposition: similar to, in the same way as. Always followed by a NOUN or PRONOUN, never by a clause with a verb. "She sings like a professional" = like + noun. "He looks like his father" = like + noun. "Like me, she prefers tea" = like + pronoun. Also expresses likes: "I like coffee" = I enjoy coffee.
He speaks English like a native — nobody would guess it is his fourth language.
The new product looks like a regular notebook but contains advanced AI features inside.
Like her mentor, she believes that preparation is more important than talent alone.
Conjunction/preposition: (1) As a conjunction: introduces a CLAUSE with a verb. "She did it as I expected" = as + clause: "I expected". "Do as I say" = do what I say. (2) As a preposition: in the role of, in the capacity of. "She works as a teacher" = in the role of a teacher. "As a student, I had no money" = in that capacity. Key distinction: LIKE = similar to (comparison). AS = in the role of / just as (function or clause).
She managed the project exactly as the manual specified — every step followed in the correct order.
He has worked as a financial analyst for eight years and recently moved into a senior advisory role.
As the team leader, she was responsible for coordinating all the moving parts of the launch.
Common mistake
Most common error: using "like" where "as" (conjunction) is needed. "She did it like I expected" — INCORRECT. "I expected" is a clause with a verb, and "like" cannot introduce clauses with a verb. Correct: "She did it AS I expected." Advertising has normalized this error: "Winston tastes good like a cigarette should" (famous 1950s slogan) should be "as a cigarette should". Second error: "She works like a teacher" (implies she ACTS SIMILARLY TO a teacher, perhaps she is not one) vs "She works AS a teacher" (SHE IS a teacher, works in that role).
Trick to remember it
Key question: does what follows have a VERB? Yes = AS (conjunction). "She did it ___ I told her" — "I told her" has a verb = AS. No verb after it = LIKE. "She did it ___ a professional" — "a professional" is only a noun (no verb) = LIKE. Second test: is it a ROLE or FUNCTION? "She works ___ a teacher" = it is her job/role = AS. Is it a SIMILARITY COMPARISON? "She teaches ___ a natural" = similar to someone natural = LIKE. Summary: clause with verb = AS. Noun/pronoun alone = LIKE. Role/function = AS.
Quick rule
Like + noun/pronoun (similarity comparison). As + clause with verb (just as, the way that) or + noun indicating role/function (in the capacity of).
Did you know?
In colloquial American English, "like" as a conjunction (before clauses with a verb) is so common that linguists consider it a grammatical change in progress. "It was like I expected" (incorrect in formal standard) is universally accepted in everyday speech. Additionally, "like" has acquired a completely new use in modern American English as a discourse marker: "She was like, I don't know, and I was like, totally." This "like" is neither a comparison nor a preposition — it is an informal quotation marker that did not exist before the 1980s.
Exercise 1 · Pick the right one
She managed the negotiation exactly _____ her mentor had taught her — patient, methodical, and never rushed.
Exercise 2 · Pick the right one
He moves on stage _____ a professional dancer — fluid, precise, and completely comfortable in front of the audience.
Exercise 3 · Form the word
Like + noun/pronoun (similarity comparison). As + clause with verb (just as, the way that) or + noun indicating role/function (in the capacity of).
Most common error: using "like" where "as" (conjunction) is needed. "She did it like I expected" — INCORRECT. "I expected" is a clause with a verb, and "like" cannot introduce clauses with a verb. Correct: "She did it AS I expected." Advertising has normalized this error: "Winston tastes good like a cigarette should" (famous 1950s slogan) should be "as a cigarette should". Second error: "She works like a teacher" (implies she ACTS SIMILARLY TO a teacher, perhaps she is not one) vs "She works AS a teacher" (SHE IS a teacher, works in that role).
Key question: does what follows have a VERB? Yes = AS (conjunction). "She did it ___ I told her" — "I told her" has a verb = AS. No verb after it = LIKE. "She did it ___ a professional" — "a professional" is only a noun (no verb) = LIKE. Second test: is it a ROLE or FUNCTION? "She works ___ a teacher" = it is her job/role = AS. Is it a SIMILARITY COMPARISON? "She teaches ___ a natural" = similar to someone natural = LIKE. Summary: clause with verb = AS. Noun/pronoun alone = LIKE. Role/function = AS.
Bryan López
Founder of SpeakUP Academy