学生はおおぜいきましたか。
いいえ、3人しか来ませんでした。わたしとトムさんとアンさんです。
Can you give more example in which しか is used so that I can understand it?
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.
Sign up to join this community学生はおおぜいきましたか。
いいえ、3人しか来ませんでした。わたしとトムさんとアンさんです。
Can you give more example in which しか is used so that I can understand it?
My general gloss for しか is "other than", or "non-". It is a strongly negative polarity item; it will only be seen in combination with a verb in negative form.
Here, other-than three people (人) did not come (来 + ません + でした, conjugated formally; the informal version is 来なかった). With quantities, specifically, we interpret that more than three people did not come. In other words, only three people came (i.e., we excluded the possibility of it being more than that).
This also explains the idiom しかない: it is simply a combination of しか with the negative adjective ない. Thus: 猫しかない -> "cat -other-than does-not-exist" -> "(it) must be a cat"; 立つことしかない -> "stand-up -act-of -other-than does-not-exist" -> "(you) only need to stand up".
Here, 「しか」 means "only". So, the word is emphasizing how "only three people came." Another example of 「しか」 being used in this context is 「今、財布に500円しかありません。」 where 「しか」 emphasizes how "only 500 yen" is in the wallet.