所謂的「不定代名詞」（indefinite pronoun），就是用來指稱不定數量事物的代名詞：Some of the books are interesting.
多數的不定代名詞都可以當作形容詞使用，後面直接加上名詞，此時便稱為「不定形容詞」（indefinite adjective）：Some books are interesting.
名詞有可數與不可數之分，修飾名詞的不定形容詞也有可數與不可數之分，用以搭配名詞的數量。例如：
Many +可數名詞： I have many friends/books/problems/shoes.
Much +不可數名詞： There isn’t much money/paper/time/coffee.
Some + 二者皆可： There is some fruit on the table.
There are some books in my bag.
A lot of +二者皆可: There are a lot of American tourists in Paris.
She has a lot of time on her hands.
