Used before nouns and noun phrases that denote a single but unspecified person or thing.
예문
1. a murder (살인 사건) 2. in a sense (어떤 의미로는) 3. She has such a wonderful voice. (그녀는 목소리가 썩 좋다) 4. for a week (1주간) 5. He charges 100 dollars an hour. (그는 한 시간에 100달러를 청구한다)
