The words "like" and "as" are often confused. It's important to understand the difference in their usage.
Like is a preposition. We need it to talk about similarity when we compare two things and or give examples. There is a noun or a pronoun after "like" (like me, like them, like a hero, like a tiger).
Everything seemed unreal, like in a dream. = similar to a dream WRONG as in a dream
Her eyes were shining like diamonds. = her eyes could be compared to diamonds WRONG as diamonds
He's like his father: hard-working, reliable, helpful. = he has a lot in common with his father WRONG as his father
I keep away from places like McDonald's. = places similar to McDonalds WRONG as McDonald's
People like you have always inspired me. = people similar to you WRONG as you
We can also use "as" for comparison. But "as" is a conjunction and it links two clauses. That's why there are a subject and a verb after "as".
He was half an hour late, just as I expected. WRONG like I expected
Please do exactly as we agreed. WRONG like we agreed
Nobody loves you as I do. WRONG like I do
In spoken English, you will often notice that people tend to use "like" instead of "as" in such examples. However, it is formally wrong.
When else to use "as"
as = because, while (when)
As a conjunction, the word "as" has several meanings. We use it to explain the reason or to show that two actions were happening at the same time. There are a subject and a verb after "as".
As it was very late, I went straight to bed. = I went to bed because it was late
As I didn't know anything myself, I couldn't tell you anything. = I couldn't tell you because I didn't know anything
As Roger has always been good at maths, he decided to study data science. = He decided to study data science because he has always been good at maths
As I was walking along the river, I saw a fisherman. = I saw him when I was walking along the river
As the plant grew, its colour changed. = The colour of the plant was changing in the process of its growth
as = in the capacity of, in the function of
We use "as" when we speak about professions, positions, functions of things.
Inesse works as a business analyst.
As your mother, I have the right to interfere.
The house was used as a military hospital.
He uses trash as a material for sculptures.
It is very easy to see the difference between like and as with the help of this example.
In these stressful conditions, he acted as a boss. (he is really the boss)
In these stressful conditions, he acted like a boss. (he isn't the boss)
as ... as
We put an adjective or a quantifier between as...as to make a comparison.
I don't drink as much tea as Phillip does. = I drink less tea than him
Ron is as tall as George. = They are of the same height
You read twice as many books as me last year. = I read half as many as you did
Besides, there are a few set expressions with "as":
- as always
- as usual
- the same as
- such as
We put "like", not "as" after the verbs look, feel and smell. It doesn't matter what goes after, a noun or a clause.
It looks like we are missing some details.
I feel like I know that woman.
It feels like November although it's August.
It smells like fresh-cut grass.