AS vs LIKE

As

1: 'As' can mean 'because/since'.

• As it was raining, we didn't go out.

2: 'As' can mean 'while' or 'at the same time':

• As I was walking down the street, I saw Jimmy.

3: We can use 'as' to talk about the way one thing is similar to another thing. In this case 'as' is a conjunction and needs to be followed by a subject and a verb or by a prepositional phrase. We invert the subject and the verb when using a formal register.

• James loves pets, as do I.

4: We need to use 'as' with expressions like 'as much as' and by 'as +adjective +as'. This is also talking about similarity. These expressions can be followed by a subject and a verb or a noun or preposition.

• John loves spicy food as much as I do.
• Lily travels as much as me.
• She's as clever as her sister is.
• London's not as big as Mexico City.

5: 'As' can be used with a noun to show someone's position. This is especially common with jobs. In a similar way, 'as' can also be used to show something's function (what we are using it for). It must be followed by a noun.

• She works as a teacher.
• Don't use the knife as a screwdriver.

Watch out! You can't use 'like' for someone's real job. You need to use 'as'.

• I work like a waitress.

Like

1: 'Like' can be used to give examples. It means the same as 'for example' and is usually followed by nouns or pronouns.

• Western European countries like France and Spain have high unemployment at the moment.

2: We can also use 'like' to talk about how one thing is similar to another thing. Here 'like' is a preposition and is followed by a noun or a pronoun.

• John loves spicy food, like me.
• Tokyo is a busy and exciting city, like London.

When we're talking about how things are similar, we often use 'like' with verbs such as 'look', 'sound' and 'smell'.

• She looks like her mother.
• It looks like rain.
• That sounds like a car.
• The kitchen smells like lemons.

'Like' vs 'as' for similarity

Often, we can use both 'as' and 'like' to talk about similarity.

• I love coffee, like Julie.
• I love coffee, as Julie does.

We need to follow 'as' with a clause (a subject and a verb). When we use 'as' for similarity, it's not followed by a noun or pronoun.

• I love coffee, as Julie.

However, when we use 'as' to mean a role or job (it's followed by a noun in this case), then we can't use 'like'. Instead, 'like' is talking about similarity.

• As your mother, I'm telling you not to go out now. (I am your mother and I am telling you this in my role as your mother.)
• Like your mother, I'm telling you not to go out now. (I'm not your mother, but I am telling you the same thing as she is. I am acting in a similar way to your mother.)

Here's another example.

• She works as the manager (= she is the manager).
• She works like the manager (= she isn't the manager, but she works in a similar way to the manager).