Watch Out For Czechlish: Who
There are a lot of common grammar mistakes that Czech speakers make in English. Here's one example that you should try to avoid.
The word “who” in English is never a noun. It is either a question or a relative pronoun. Here are some examples:
Who is coming to the party?
She's the one who baked the cake.
However, this sentence is not correct:
Who studies hard will do well on the test.
That's because in this sentence, who is used as a noun. But that's not its job! To say this sentence in English, you have to add something, such as someone, anyone, a person, a student, or another noun for the subject:
A student who studies hard will do well on the test.
There we go. Now who is being used as a relative pronoun, just as it should be.
How can you keep track of all this? Fortunately, there's an easy rule to remember: who should never be at the start of a sentence. It can only be at the start of a question, or in the middle of a sentence. Remember that rule, and you'll be talking like a native speaker in no time!