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 the modern 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.