I was reading a Japanese novel on my Kindle last night when I came across the word 適当 (てきとう) being used to mean "suitable" or "appropriate."

I was a bit thrown off for a second. Although I hear the word 適当 (てきとう) being used quite frequently in spoken Japanese, I rarely hear it being used with this meaning.

It reminded me of a few challenges I've had with the word 適当 (てきとう) over the years...

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適当（てきとう）

Long ago, when I was only learning Japanese from books and had no Japanese friends, I learned that 適当 (てきとう) means "suitable" or "appropriate."

For example, it could be used in a sentence like this:

ロミオ役に適当な人が見つからない。
ロミオ　やく　に　てきとうな　ひと　が　みつからない。
We can’t find a suitable person to play the part of Romeo.
Literally: “the part/role of Romeo + に + suitable + person + が + has not been found (→ cannot find).”

適当な人 → suitable person

That made sense to me, and I even came across 適当 being used this way in a number of learning resources.

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テキトー

Fast forward to just a little while after I had moved to Japan.

I was with Rei on one of our dates, and she used the word 適当 (てきとう) in a way that didn't make any sense to me. I don't remember exactly what we were talking about, but let's pretend that we were having this conversation:

A:
ズボンはどうやってたためばいい？
ズボン　は　どうやって　たためばいい？
How should I fold the pants?
Literally: “pants + は + how + should fold (=if fold + good)?”

B:
テキトーでいいよ。
テキトー　で　いい　よ。
Just any way is fine.
Literally: “halfhearted / half-baked + で + good + よ.”

Just fold the pants suitably? What's that supposed to mean?

As you can see from this conversation, sometimes the meaning of 適当 is nothing like "suitable" or "appropriate." If anything, it's closer to something like "half-baked" or "halfhearted." I'm going to refer to this meaning as "negative 適当."

Personally, I don't like the translations "half-baked" and "halfhearted" for "negative 適当," as they don't seem to capture the nuance and versatility of this word.

For example, "negative 適当" can even be translated as "irresponsible" or "careless:"

あいつは本当に適当な奴だ。
あいつ　は　ほんとうに　てきとうな　やつ　だ。
He’s so irresponsible.
Literally: “that person + は + truly + irresponsible / halfhearted + person + だ.”

As I got more and more exposure to Japanese, I learned that "negative 適当" is much more commonly used in Japanese conversation than "suitable 適当."

I also found out that katakana is commonly used when writing "negative 適当," as we saw in our first example of it above.

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Here's an example of "negative 適当" being used as an adverb (since 適当 is a na-adjective, we put に after it to make it into an adverb):

適当に書いた作文なのに、先生にめちゃめちゃ褒められた。
てきとう　に　かいた　さくぶん　なのに、　せんせい　に　めちゃめちゃ　ほめられた。
I barely put any effort into my essay, but the teacher was super impressed with it.
Literally: “halfhearted / half-baked + に + wrote + essay + なのに (=although), + teacher + に + extremely + was praised.”
Note: You'll see that the literal breakdown differs quite a bit from the translation. Sometimes things just don't match up very well. ^^

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適切（てきせつ）

So, is it OK to use 適当 when we want to say "suitable?"

Sure. But it might be more common to hear the word 適切 (てきせつ) in this case, which means something like "appropriate."

For example, I'm currently doing a proofreading job for a company that is publishing an English textbook for Japanese high school students. In one of the question-and-answer sections of the book, the authors write:

それぞれの選択肢から適切なものを選びましょう。
それぞれ　の　せんたくし　から　てきせつな　もの　を　えらびましょう。
Choose the (most) appropriate answer from each of the selections below.
Literally: “each + の + choices / selection / options + から (=from) + appropriate + thing + を + let’s choose.”

That sentence we saw earlier with "suitable 適当" also could have used 適切：

ロミオ役に適切な[適当な]人が見つからない。
ロミオやく　に　てきせつな　[てきとうな]　ひと　が　みつからない。
We can’t find a suitable person to play the part of Romeo.
Literally: “the part/role of Romeo + に + appropriate [suitable] + person + が + has not been found (→ cannot find).”

Or take this sentence, for example:

シャワーに適切な[適当な]温度は40度くらいです。
シャワー　に　てきせつな　[てきとうな]　おんど　は　よんじゅうど　くらい　です。
About 40 degrees is a suitable temperature for a shower.
Literally: “shower + に + suitable / appropriate + temperature + は + 40 degrees + about + です.”

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I guess the moral of the story is that we should be a bit careful about learning Japanese from dictionaries and run-of-the-mill grammar books. They sometimes play down the importance of everyday spoken Japanese.