ПРЕ_ДОПРЕДЕЛЯЮЩИЕ СЛОВА   -   PRE-DETERMINERS

SUCH, WHAT, RATHER, QUITE

These words are normally placed before the indefinite article.
Such and what are often used to express surprise or other emotions:

Examples:

a. What a lovely day!
b. She's such a lovely woman!
c. What an incredible film!
d. He's such a fantastic guitarist!

Rather and quite are 'commenting' words, referring to the degree of a particular quality. They can express disappointment, pleasure, or other emotions, and are used before a/an + adjective + noun:

Examples:

a. It's rather a small car. (= I'm a bit disappointed because it's small)
b. It was quite a nice day.(= I was agreeably surprised.)
c. He's had quite a bad accident. (= I'm worried)
d. I've just met rather a nice man. (= I'm pleased)