First, the phrasal verb and the one-word verb might not be exactly the same.
For example, what does install mean? What things can you install?
You can install household goods, like washing machines or air conditioners. You can also install software on your computer or on your phone.
The phrasal verb put in only has the first idea: you can put in a new washing machine, but you can’t put in a new app or put in a new operating system.
Secondly, the phrasal verb and the one-word verb often have different registers.
What does that mean?
It means they’re used in very different situations.
Let’s see why this matters:
D: Hi, Maria! Glad you could attend!
M: Sorry for appearing so late. I boarded the wrong bus and then I was wandering for ages seeking your street.
D: Don’t worry about it.
M: Should I remove my shoes?
D: If you don’t mind. Would you like something to drink before we depart? Tea? Coffee?
That was part of the same dialogue you heard before. How was it different? Did it sound natural to you?
This time, we used one-word verbs instead of phrasal verbs in many places. I hope you heard that the dialogue sounded very strange and unnatural.
For example, a native speaker would almost never say sentences like these:
Glad you could attend!
Sorry for appearing so late.
I boarded the wrong bus.
I was seeking your street.
Should I remove my shoes?
Would you like something to drink before we depart?
The one-word verbs are too formal, and they aren’t used in simple, spoken English like this. You need to use the phrasal verbs.
Glad you could come along!
Sorry for turning up so late.
I got on the wrong bus.
I was looking for your street.
Should I take off my shoes?
Would you like something to drink before we head off?
Even when phrasal verbs and one-word verbs have the same meaning, you can’t always use them in the same way. Look for and seek have the same meaning, but seek is much more formal and literary. You wouldn’t use it often in conversational English.
So, in spoken English, you often need to use phrasal verbs to sound natural.
On the other hand, because many phrasal verbs are more informal, they aren’t appropriate in formal writing.
That said, many English learners think that ‘all phrasal verbs are informal’. That isn’t true. Phrasal verbs can be more formal or informal like any other words.
For example, pop out is very informal; you probably wouldn’t use it in written English. Look for has a neutral tone, meaning you can use it in any situation.
Some phrasal verbs, like draw upon, even sound quite formal.
However, when you have a phrasal verb and a one-word verb with the same meaning, like turn up and arrive, the one-word verb is generally more formal than the phrasal verb.
Now, you should know what phrasal verbs are, how they’re different from ‘normal’ verbs, and when you should use phrasal verbs.