The word such is very useful but tricky because it has several different forms and meanings. Intermediate- and advanced-level students can use such in these ways:
1. Such intensifies the meaning of a noun phrase and is normally followed by an indefinite article (a, an) and a singular countable noun, or no article and an uncountable noun or plural countable noun.
That’s such a good idea!
I didn’t know she had such muscles!
The train travels at such high speed.
2. Such with a noun phrase can also form part of the structure such … that. This has the meaning of a result: the dependent clause happens because of the noun with such in the main clause.
My cell phone takes such good photos that I no longer use a camera.
There was such a storm last night that the river flooded.
3. Such can also have the meaning of this type of or these types of. Writers use such in this way to create cohesion between sentences and paragraphs.
The children were dancing on the tables. Such behavior is not acceptable in school.
The company had to cut costs without reducing productivity. Such a dilemma is typical of growing businesses.
It is important for students to remember that such is not a determiner. That means it does not replace the article (as a pronoun like this or that does). Such always introduces the noun phrase. It cannot be used in the position of an adjective.
INCORRECT: A such problem is unusual.
INCORRECT: Such problem is unusual.
CORRECT: Such a problem is unusual.
In addition, such cannot be used with the definite article (the) because it always has an indefinite meaning: such a problem means a problem like this one, not exactly the same as this one.