A different way to join i-adjectives

Question

I originally learned that i-adjectives are joined with くて e.g.

長くて、赤い魚が欲しい。

I want a long, red fish.

Recently I've come across a couple of examples where the two adjectives are joined together with the omission of the い from the first e.g.

細長い四角

Thin, long rectangle

Is this something I can do with any pair of i-adjectives or just ones of the same type (ones that describe size in this case), or are there only specific pairings that are allowed?

Answer 1

As a general rule, you cannot freely join two arbitrary adjectives like this. You can't say 長赤い nor 赤長い.

Words like 細長い are sometimes called 複合形容詞 (compound adjective). Here are some examples:

• 青白【あおじろ】い (pale), 青【あお】い + 白【しろ】い
• 赤黒【あかぐろ】い (dark red, bloody), 赤【あか】い + 黒【くろ】い
• ずる賢【がしこ】い (sly), ずるい + 賢【かしこ】い
• 暑苦【あつくる】しい (muggy), 暑【あつ】い + 苦【くる】しい
• 面白【おもしろ】おかしい (funny), 面白【おもしろ】い + おかしい

Basically these words have their own entries in dictionaries.

But once in a while Japanese people coin new words using this rule. For example young people sometimes say キモかわいい (gross but cute), which is a fairly new i-adjective made of キモい and かわいい.