ことになってる VS はずだ

[reverser]

As stated in the title, can someone please shed some light on the difference between the following expressions:

学校に行くはずだ。

AND

学校に行くことになってる。

They share almost identical definitions in any dictionary, and even asking native Japanese speaker friends has yielded no results. They feel they are mostly the same, but there could be some subtle nuances that they can't explain or bring to words.

Any help is greatly appreciated.

Thanks,

Mike

[QuackingShoe]

This question kindof confuses me, because they're really pretty different in my experience.

はず is used to describe what's expected or what aught to be, given the situation and the information you have. "He should be going to school (based on what we know, based on our expectations)." It's often used when expressing mild surprise/disfavor when things are contrary to expectation. "He should have gone... (I thought he was going to)"

ことになる means that it's been decided, or it's come to be that, a certain thing will happen. It's intent isn't to express what's expected to be, like はず, but what is simply going to be because that's how things have turned out. "It's been decided he'll go to school/It's come to be that he'll go to school."

[Javizy]

What dictionary do you use? Like QuackingShoe, I don't see the similarity between the expressions. Are you literally using a dictionary, or a grammar dictionary? You might want to check out A Dictionary of Basic Japanese Grammar, because you'll probably have a nightmare trying to distinguish the different conditionals, among other things, if you're relying on a J-E dictionary.

[reverser]

教えってくれて、ありがとうございました。辞書だけを使っていません。そうですけれど、僕には、この文法がちょっと難しんです。でも、みんなさんのお陰で、今よく分かっています。

お世話になりました。

マイク