As — role, function, or clause comparison
| Use | Example |
|---|---|
| Role / function (= in the capacity of) | She works as a nurse. · He used the box as a seat. · As a child, I was shy. |
| Clause comparison (+ subject + verb) | Do as I say, not as I do. · Leave it as it is. |
| Fixed phrases | As usual, he was late. · As expected, it rained. · As well (= also). |
Like — similarity or comparison with a noun
| Use | Example |
|---|---|
| Comparison with a noun/pronoun (= similar to) | He looks like his father. · She sings like a professional. |
| Feel / seem / taste / sound + like + noun | It feels like rain. · This tastes like chicken. |
| Informal "such as" (giving examples) | Sports like tennis and swimming are great for fitness. |
As if / As though — hypothetical comparison
As if and as though introduce a hypothetical comparison — you are describing how something seems or looks, not stating a fact.
| Form | Meaning | Example |
|---|---|---|
| as if / as though + past simple | Unreal / imagined (unlikely to be true) | She acts as if she owned the place. (she doesn't) |
| as if / as though + present/past | May or may not be true | He looks as if he's seen a ghost. (maybe true) |
Common confusions
| Common mistake | Why it's wrong | Correct |
|---|---|---|
| ✗ "She works like a nurse." (function) | Like cannot express a role or function | She works as a nurse. |
| ✗ "Do like I say." (clause + verb) | Like is not followed by a full clause in formal English | Do as I say. |
| ✗ "He looks as his father." (appearance comparison with noun) | As alone cannot compare appearance with a noun | He looks like his father. |
Informal vs formal:
In informal speech, "like" is often used where "as" would be more correct: "Do like I say" (informal) vs "Do as I say" (formal). In writing and exams, prefer as for clauses and roles.
Exercises
Choose as or like.
1. She trained ___ a doctor for six years.
2. He looks exactly ___ his grandfather.
3. ___ I said before, the project needs more time.
4. It looks ___ it's going to rain soon.
5. She acts ___ if she's never made a mistake in her life.