friend、mate、acquaintance与pal这些名词都有“朋友”之意。
friend : 一般用词，指某人喜爱并乐意与之相交往的人。
- She's my best/oldest/closest friend - we've known each other since we were five.
她是我最要好／交情最久／最亲密的朋友——我们5岁的时候就认识了。 - He's a family friend/friend of the family.
他是全家人的朋友。 - This restaurant was recommended to me by a friend of mine.
这家餐馆是我的一个朋友给我推荐的。 - We've been friends for years.
我们已是多年的朋友了。 - José and Pilar are (good) friends of ours.
何塞和皮拉尔是我们的（好）朋友。 - We're (good) friends with José and Pilar.
我们和何塞、皮拉尔是（好）朋友。 - She said that she and Peter were just (good) friends (= they were not having a sexual relationship).
她说自己和彼得只是（好）朋友而已。 - I've made a lot of friends in this job.
我从事这项工作结交了很多朋友。 - He finds it difficult to make friends.
他发现交朋友很难。
mate : 最普通用词，既可指好友、同事，又可指合伙人，还可指配偶的一方。
- We've been mates since our school days.
我们从学生时代起就是朋友。 - She's my best mate.
她是我最好的朋友。 - Have you got the time, mate?
老兄，你知道几点了吗？
acquaintance : 指彼此相识，但交往不甚密切，相互间没有深厚情感的人。
- a business acquaintance
在生意上打过交道的人
pal : 口语用词，指十分要好的朋友。
- You're my best pal.
你是我最好的朋友。 - It's my old pal Pete!
那是我的老友皮特！
