Hazu vs. tashika ni

Sorry to bother you all once again but i have another question i need some help with. My wife is actually Japanese but for some reason she struggles actually explaining the differences with some things.

はず　と　確かに　 sound almost the same to me.

Please take a lot at these sentences.

To me, both of these sound exactly the same - to say (surely there is someone up there, there must be someone up there, it must be a big dog, im sure i said that etc.)

Please help me im pulling my hair out!


確かにもう言った
もう言ったはずです

確かに上にだれかいる
上にだれかいるはずです

確かに大きい犬です
大きい犬のはずです

Thank you

Hi dcd

you might want to get the "dictionaries or Japanese grammar" books if you are looking at these kind of explanations. These books give normally quite detailed descriptions with example sentences and sometimes comparisons between different structures.

However, if your wife says that for her there is no notable difference, than that is obviously also just fine. Language doesn't work like maths and the more you advance, the more will be by "feeling" what sounds natural and what doesn't. But this feeling will only develop gradually over (long) time.

I personally don't think that 確かに and はずare terribly similar. Again, I am not Japanese so might be misleading you completely. 確かに for me is more like "as a matter of fact", "now that you say it..." type of expression, while はず is a percentage of probability.

Last but not least, I think there are also forums out there more dedicated to Japanese grammar, so probably you will find better / more / quicker answers there rather than on this forum here, which is much more geared towards travelling / living in Japan rather than language.

But keep picking our brains by all means.

They are quite different :)

確かに上にだれかいる。 = For sure there is someone up there.
You KNOW that there is someone; you saw someone.

上にだれかいるはずです。= There must be someone up there. There should be someone up there.
You believe there must be someone, because you heard some noise, but you don't KNOW.


確かに大きい犬です。 = It certainly is a big dog (it would be a phrase you would say if you heard that your friend has a big dog, and you go to that friend's house and see for yourself that the dog REALLY is big, with the dog right in front of you). So for sure you KNOW.

大きい犬のはずです = It must be a big dog/should be a big dog.
This can be said in different situations; you are assuming/estimating that it is a big dog, though you haven't seen it. "My friend said he has a mastiff, so (his dog) must be a big one."


When it comes to 確かにもう言った　もう言ったはずです, relating to things "you" believe "you" did, there is no way to verify it, right? (unless someone was recording your whole conversation).

Both are expressions of strong subjective judgements.
The difference consists in that 確かに means “conviction” or “affirmation” which might happen to be close to the reality, while 〜はず remains “conjecture” in spite of self conviction.

Thank you for the replies everyone.

The usage between the two is definitely different. I'm sure you understand the difference by now, but just to add, another example I can think of is this:

A1: I thought you received a parcel for me. Where did you put it?
B1: もう言ったはずです (I already told you, for sure.)
A2: No, you didn't. Where is the parcel?
B2: もう何度も言ったはずです (I surely told you many times already.)
A3: No, you didn't!
B3: 確かにもう言った (I'm sure I already did.)

You can't say B3 in the order of B1.