2781
My Japanese text book says that a present-tense verb followed by ことにする is used
to indicate making a decision about the action. But I've also noticed the verb
決める, and that it's usage is very similar.

So supposing we have a sentence such as:

朝ご飯を作った後に、ジョギングすることにした。(After making breakfast, I decided to jog.)

My question is, would there be any specific semantic difference if 決める was
used? In all the cases that I've seen, the final する has always been in the
past-tense, but 決める has been in a variety of forms; is this possible
difference of the two?

Thanks! :)
CC BY-SA 3.0
2011-08-21T00:54:23.733
2772
2019-10-03T12:27:02.567
636
question
word-choice
ことにする vs. ことに決める
Using your example sentence as a guideline, the difference is this:

With `ことにした`, you have decided to jog, and you _might_ have jogged. `ことにする`
_implies_ action taken. Usually in the sense that you habitually do it.
However, you might just mean you've made a decision.

With `ことに決めた`, you have decided to jog, but whether or not you have jogged yet
is an open question. You have only conveyed your intentions. It strictly
_only_ refers to a decision with no implication of action.
CC BY-SA 3.0
2011-08-21T05:22:48.500
2780
2011-08-21T06:52:46.997
2011-08-21T06:52:46.997
119
119
2772
answer
This is what "A Dictionary of Basic Japanese Grammar" has to say on the matter
of ことにする vs ことに決める:

> _Koto ni suru_ and _koto ni kimeru_ 'determine to do s.t.' are virtually
> identical in meaning. The difference is that the former is an idiom and,
> therefore, frequently used in colloquial speech, while the latter is
> appropriate when the speaker is talking about a relatively important
> decision in a rather decisive manner. Also, _koto ni suru_ can be used to
> mean 'I hereby decide to ~' but _koto ni kimeru_ cannot. Thus, [1] below
> cannot be rephrased by _koto ni kimeru_.
>
> [1] 私は会社をやめることに **します** /???きめます。  
>  _Watashi wa kaisha wo yameru koto ni shimasu /???kimemasu._  
>  (I've decided to quit my company.)
CC BY-SA 4.0
2011-08-21T05:54:19.463
2781
2019-10-03T12:27:02.567
2020-06-17T08:18:27.500
-1
108
2772
answer
ことにする vs ことになる is equal ことに決めた

私は会社をやめることにします。（自分が決めた） I've decided to quit my company.
私は入院中はタバコをやめることに決めた。（他人（医者が決めた））is equal 私は入院中はタバコをやめることになった。（他人（医者が決めた）） I
had to abstain from smoking while I was in the hospital.
CC BY-SA 3.0
2011-08-22T04:58:22.833
2789
2011-08-22T04:58:22.833
619
2772
answer