Такой (такая, такое, такие) / так

In my experience, even high level students sometimes make mistakes when it comes to the choice between "такой" and "так". Here're some simple rules to help you distinguish between them:

1) "Такой (такая, такое, такие)" are used to describe nouns or adjectives (and usually go before them) :

Эти ботинки такие хорошие! = These shoes are so good!

Он не сделал бы этого, он не такой человек. = He wouldn't do that, he isn't that kind of person.

They are also used in the following expressions:

Что это такое? = What is this?

Кто он (это) такой / Кто она такая / Кто они такие? = Who is he (that) / Who is she / Who are they?

2) "Так" is used to describe adverbs or verbs (and usually goes before them):

Нельзя так работать. = You can't work like this.

Она так хорошо говорит по-русски! = She speaks Russian so well!

"Так" can also be used at the end of the sentence:

Это так? = Is it so?

Сегодня всё не так. = Today everything goes wrong.

Practice: try this exercise