In any basic Japanese textbook you likely be taught about the ’こそあど’ words, which refer to something that is ‘close’ (either emotionally or physically), ‘far’, ‘very far’, or ‘uncertain’ (respectively). For example, the below set of four are probably the easiest to grasp as a beginner:
- これ – this
- それ – that
- あれ – that over there
- どれ – which
These are pronouns (代名詞) and are treated pretty much like english pronouns, for example:
- それが欲しい
- I want that.
The following four words also have similar meanings:
- こう
- そう
- ああ
- どう
The major difference with these, however, is that they are adverbs (副詞）.
I don’t think there is a single word in English to express these, but you can get a feel for them by thinking in terms of ‘in this way’, ‘in that way’, etc.
The tricky part now is learning which to use which set of words. For example, let’s take this simple English sentence:
- I said that.
The best answer is to use そう, like this:
- 僕はそう言った
So why is this the correct answer? I wouldn’t go as far as saying that “僕はそれを言った” is, strictly speaking, grammatically incorrect, but using そう here is the most natural and you’ll hear it most if not all of the time. Let’s look at a few more examples before we draw a conclusion about why そう is best here.
- He also thinks so.
- 彼もそう思ってる(でしょう)。
The above one is easy to remember because of the coincidence between the english ‘so’ and Japanese ‘そう’.
- Yeah, let’s do that.
- うん、そうしよう。
This could be the response of someone saying 買い物に行かない？ (do you want to go shopping?), where you just want to agree with what they are proposing. The phrase “それにしよう” is actually natural Japanese as well, but is typically used to refer to something more specific, like “Let’s choose that one” when looking at a few types of deserts in a display case.
What if you wanted to say the following:
- *That’s* a good idea
How would you say it in Japanese?
- それがいい（ね） (you could use a word like 考え to explicitly say ‘idea’ but I think that’s less natural)
It’s important to note that ”そうがいい” would be incorrect grammar and sound very unnatural, since you can’t make an adverb a subject of a sentence.
One more example:
- My dad bought that.
- お父さんはそれを買った.
Using “そう買った” would be very unnatural here.
After looking at these examples I’ll agree it’s a bit tricky to give a formula for exactly which set of words to use. However I think these guidelines will be a good start:
これ／それ／あれ／どれ
- Often used when referring to something specific, like a physical object.
- Used for the subject of the sentence
こう／そう／ああ／どう
- Used when you want to describe something abstract (like something being thought)
- Used when describing ‘in this way’, ‘in that way’, etc., basically how something is done.
- Commonly used with verbs 言う、思う、考える and similar verbs (語る, 仰る, etc.)
Guidelines like this are always nice, but eventually you’ll learn a bunch of phrases that contain these words and pick from your personal lexicon during much of your speech and writing.
Notes
There are a few set phrases using して and the こそあど words that are good to remember.
- こうして “like this”, “in this way”
- そうして “and then” (Can be used at the beginning of a sentence without a subject, like “そして、。。。”)
- どうして “why” (The explanation for this one is quite tricky and I may attempt it in a another post, but for now just remember it as is)
One final expression that is a bit tricky. You might think that “What do you think?” in Japanese is ”なに思う？”, but that would be a bit off the mark. The natural phrase for this is “どう思う” and you can remember this as “in what way do you think?” or “how do you think?”.
References
https://kotobank.jp/word/こそあど-501943
really helpful