Phrasal verbs are very common in English, especially in conversation. They are formed with a verb and one, or sometimes two, particles.
There are two main types of phrasal verb: separable and inseparable.
1. Separable phrasal verbs
With separable phrasal verbs, it is possible to have the verb and particle apart or together:
She put her sweater on. OR She put on her sweater.
However, if a personal pronoun (her, it, my, etc,) is used the verb must be separated from the particle. (The pronoun must be in the middle – it cannot go after the particle.)
She put it on. She put on it.
2. Non-separable phrasal verbs
Non-separable phrasal verbs cannot be separated.
He took care of the problem.
I look after my elderly mother.
We need to think about who will do it.
With non-separable phrasal verbs a personal pronoun can go after the particle. It cannot go between the verb and particle.
He took care of it quickly.
I’ve looked after her for 2 years now.
Phrasal verbs that do not take an object will always be non-separable:
I get up at 7 a.m.
The plane took off at 09:30.
Phrasal verbs with two particles are always inseparable. Personal pronouns can come after the particles.
I’m looking forward to the movie.
I’m looking forward to it.
I looked in on my mother when she was ill.
3. Different particles and different meanings
One verb can often have many different particles, which usually change the meaning of the phrasal verb. Some phrasal verbs can have the same particle but more than one meaning. Some meanings may be separable, while others are non-separable.
He took on more responsibilities at work. [separable – accept a difficult task]
The company recently took on some new staff. [separable – hired, employed]
The news took on a new meaning after the interview. [separable – acquire, gain]
I took off my jacket. [separable – removed]
The plane took off. [non-separable (no object) – left the ground]
She took down her painting. [separable – removed or dismantled]
He took down a lot of notes at the meeting. [separable – wrote down]
4. How to know if a phrasal verb is separable or non-separable
Unfortunately, there are not many rules. All phrasal verbs with two or more particles are non-separable (he got on with all her friends). All phrasal verbs that do not take an object are non-separable (The plane took off). For all other phrasal verbs, you simply have to know which type they are through experience.
If you are not sure, the safest option is to never separate the verb and particle and never use a pronoun after the particle. However, this may not always sound very natural.
Why don’t you take off your sweater? > I don’t want to take off my sweater.