英语语法: 复合形容词Compound Adjective
Source: Zhihu
(prepared by: alexcwlin; edited by: Adam Lam)

Question:
In my translation 0120翻译：小熊住山洞, the title reads: “Cave-Dwelling Little Bear”.

A reader asked:
“住山洞为什么是cave-dwelling不是dwelling-cave啊 我记得床前明月光好像是bed-front moonlight is shining bright 绿绿的是light-green 想知道这个连字符到底咋用的啊”

alexcwlin comments:

1.     hyphenated adjective “cave-dwelling”

The word “cave-dwelling” is a compound word functioning as an Adjective.
[cave-dwelling是一个复合词，用作形容词]

It is made up of a Noun “cave” and an Adjective “dwelling” joined by a hyphen to indicate that the two words work together as one word.
[它由一个名词“cave”和一个形容词“dwelling”组成，用连字符连接，表示这两个词合为一个词]
(See: https://www.grammarly.com/blog/hyphen/)

Hyphenated Adjectives are very commonplace, and here are a sample of them:
[连字符形容词非常常见，这里有几个例子]

a.      10-page agreement;

b.     part-time worker;

c.      three-foot table;

d.     five-year-old boy

One trick you have to remember is in a Compound Adjective, the Noun is not usually pluralized. That is, you do not say: 10-pages agreement (Wrong), three-feet table (Wrong), and five-years-old boy (Wrong).
[你必须记住的一个技巧是，在复合形容词中，名词通常不是复数形式。也就是说，你不说: 10-pages agreement (错), three-feet table (错), and five-years-old boy (错).]