ことはない vs わけがない, しかない vs わけ

[stevesayskanpai]

These expressions seem very similar. Would the differences be accurately summed up as follows?

ことはない - no need to
わけがない - there is no reason for
しかない - no alternative, no option but to
わけにはいかない - have no other choice but

Especially the last two grammar expressions seem very similar.

Cheers!

SSK

[j_bertoni2279]

More context might help, but , for example,

行ったことはない

means more like "I haven't gone (there)".

塩しかない

"We only have salt", maybe at a dinner table.

Vわけにはいかない

"V-ing won't do, shouldn't V, etc"

My Mac seems to have disable Japanese language after I hit a random button, but I think the other one you mentioned was:

Xわけはない

It's tno that case that X is true, or not because of X. I'd have to look that up, sadly.

[mutley]

Sounds like you've pretty much got the gist of them.

..ことはない- no need to
it might commonly be used in the form
わざわざ。。。ことはない- no need to go to the trouble of doing...

。。までもない
。。までのこともない
are 2 phrases which seem to have a similar meaning




..わけがない- no reason for..., ...shouldn't be the case
i think 。。はずがない has a similar usage


...わけにはいかない- can't do something, usually due to social conventions/ common sense even though one wants to (be careful as this expresses obligation by saying what one can't do)

。。しかない- ..is the only option/method left to you

phrases like ..べきだ and しなければならない also are used to express obligation, the nuances of all are slightly different and you should probably check plenty of example sentences to get the gist of them.

彼女のせっかく作った料理だから食べないわけにはいかない
can't not eat the food out of social obligation to your girlfriend

雨が降っているので車で行くしかない。
it's raining so there is no other option but to go by car

地球を守るべきだ
expresses that the speaker thinks we have a moral obligation to (should) protect the earth

[Javizy]

ことはない - no need to or not possible. It's the same as either はずがない or 可能性がない, depending on the context.

心配することはない。
There's no need to worry.
彼女が来ることはない。
There's no chance she will come.


わけがない - there is no way (as far as you're concerned, it's impossible)

こんな複雑な文法が分かるわけがない！
There's no way I can understand this kind of complicated grammar!


しかない - no alternative, no option but to

You want to go to London, but the %$^&bag #$%^s are on strike again, so バスで行くしかない


～ないわけにはいかない - have no other choice but

You want to watch the World Cup final, but your genius friend who you've known since you were five decided to make you the best man at his wedding today, so 行かないわけにはいかない.


Kind of a rough late-night explanation, but hopefully it's useful.

[stevesayskanpai]

Thanks everyone for your replies, I think I understand them better now.

[mieth]

for the most part I think everyone covered the others. Just one note on the ni wa ikanai grammar. Its a double negative can't not do which ends up being having to do something. Of course you could add this to a non negative as well meaning that you can't do something. The thing is with this one is that you can't do something because of an external reason of some sort that is preventing from doing or not doing something. For example if you say su-ki ni iku wake ni ikanai. It means that you can't go skiing but it would probably be because you have no money or there is a storm or you got a flat tire. It has nothing to do with your ability. It is an external cause.