What is the difference between 「と」and 「時／とき」? Are they interchangeable?


From what I've seen, when 「と」or「時／とき」are used to express "when", they seem to
be interchangeable, and I can't seem to find any differences between them.
I've looked at other questions that were answered, but it didn't really
clarify things for me. I'm wondering if anyone would be able to explain the
nuance, and how it may slightly alter the meaning of a sentence. If they
aren't interchangeable, is there a way to determine the best option that a
native speaker would most likely use?

仕事から家に帰る時に、日本語を勉強する。

**VS.**

仕事から家に帰ると、日本語を勉強する。

How different would each sentence be?




The two sentences are rather different.

When you say

> 仕事から家に帰る時に、日本語を勉強する

You probably meant "I study Japanese when I go home from work." But, this is
not what the Japanese means. The Japanese says, "I will study Japanese
_before_ I return home."

> 仕事から家に帰ると、日本語を勉強する。

Captures your most likely intended meaning.

First とき really doesn't mean _when_ quite as we use it in English. It really
has more of a meaning of before/after depending on the _tense_ of the verb
preceding it.

> 帰る時 > _before_ I return home.

> 帰った時 > _after_ I got home.

When using < _S1_ >時< _S2_ >, event < _S1_ > describes the state of affairs
that define the time when event < _S2_ > occurs. Verbs of movement, like 帰る,
complicate this since they are _instantaneous_ verbs in Japanese (ie., 帰る=>"I
will return home", 帰った=>"I've returned home"). It is possible to construe

> 仕事から家に帰る時に、日本語を勉強する

as meaning, "On my way home from work, I studied Japanese." Since 帰る does not
describe a completed state of affairs, it **cannot** be construed to mean you
studied after getting home since then the act of 帰る'ing (to create an
linguistic abomination) hasn't been completed: ie., you're not home yet.

You might ask, then how is 帰るとき and 帰る前 different?

The verb 帰る generally means "to return home". 帰る時 means "before I got home"
(yes, I used past tense in English). But 帰る前 would mean something more akin to
"before I left to go home".

So, if you say 仕事から家に帰るとき、日本語を勉強する。 you could mean that on your way home you
study Japanese (on the bus or train) or you go to a language school or
something like that. You've already left work, but you haven't made it home
yet. All because 帰る hasn't been completed yet.

So, now let's revisit:

> 仕事から家に帰ると、日本語を勉強する。

I believe this would sound a bit off to a native Japanese speaker. In the
construction < _S1_ >と< _S2_ >, event < _S2_ > is not generally something that
you have control over. と shows a correlation between two events (in which case
we usually translate it as _whenever_ ). Or, it expresses a consequence
between two different events (event _S1_ having happened, _S2_ happens). But,
in either case, _S2_ isn't something you really have much control over.

So, if you want to say something like "When I get home from work, I study
Japanese" then try something like

> 仕事から家に帰ってから日本語を勉強する。

