はず, coming from the kanji
筈（はず）, is a word in Japanese that is very similar to ‘bound’ in English. This means that it expresses something that the speaker is ‘quite sure is true’, but cannot confirm. The most common translations of
はず are ‘bound to be (A)’, and ‘should be (A)’.
As
はず is a noun, it may be used in any place that a noun would usually be used. It will often be followed by
だ, or
です.
-
今日（きょう）は雨（あめ）が降（ふ）るはずだ。
It is supposed to rain today. (But I am not 100% sure if it will)
-
新幹線（しんかんせん）で行（い）った方（ほう）が速（はや）いはずだ。
It is bound to be faster if we go by shinkansen. (But I am not 100% sure if it will)
-
彼（かれ）は魚（さかな）が嫌（きら）いだから寿司（すし）は嫌（きら）いなはずだ。
He does not like fish, so he is sure to dislike sushi. (But I am not 100% sure if he will)
-
頼（たの）んだのはコーヒーのはずだったけどお茶（ちゃ）が来（き）た。
I was sure that I ordered coffee, but tea came. (But I am not 100% sure if I did)
Despite はず sometimes being translated as ‘should’, this is only when you think that something ‘should be true’, and cannot be used when making suggestions/giving advice. Due to this, ‘bound’ is the more accurate translation of 筈（はず）, in almost all situations.
The
だ (or
です) in
はずだ may be omitted. This usually makes
はず sound a little less certain, like ‘bound to be (A)... probably’. In the same way, speakers may sometimes add
はず to the end of their sentences in a similar way to 多分（たぶん）, in order to show that they are not 100% certain about whether what they just said is accurate or not.
-
ハリーも
今日（きょう）のパーティーに行（い）く…はず。
Harry will go to the party today… Probably.
-
出（で）かける前（まえ）に家（いえ）の中（なか）の電気（でんき）は全部（ぜんぶ）消（け）した… はず。
I turned off all the lights in my house before I left… I’m pretty sure.