JLPT N4 Guessing, certainty, and wondering
と思う states an opinion, かもしれない a possibility, and きっと and はずだ strong expectation; はずがない rules something out. かな and かしら voice wondering, and じゃないか・ではないか seek agreement or express realization. Learners often treat はずだ like "should" in the sense of obligation, but it only expresses expectation.
11 N4 grammar points in this group
と思う (to omou): I think that
Use と思う when you want to express I think that in a Japanese sentence.
明日は雨だと思います。 — I think it will rain tomorrow.
かもしれない (kamo shirenai): might; perhaps
Put かもしれない at the end of a statement and it becomes a possibility instead of a fact.
明日は雨かもしれません。傘を持っていったほうがいいですよ。 — It might rain tomorrow. You’d better take an umbrella.
きっと (kitto): surely; certainly
きっと marks a strong guess, somewhere around 80–90% sure. It often softens into warm encouragement, because telling someone “you’ll surely pass” is both a prediction and a kind word.
田中さんはきっと来ますよ。 — Tanaka will come, I’m sure of it.
はずだ (hazu da): should be; expected to be
The noun はず means “expectation” or “what ought to be the case.” はずだ (polite: はずです) turns a sentence into a confident expectation.
田中さんは三時の電車に乗ったから、もう着いているはずです。 — Tanaka caught the three o’clock train, so he should be there by now.
はずがない (hazu ga nai): there is no way that
はず is a noun meaning roughly “expectation” or “what logically follows.” はずがない is literally “there is no expectation (that ~).
彼が約束を忘れるはずがありません。 — There’s no way he’d forget his promise.
さすが (sasuga): as expected
Use さすが when you want to express the N4 idea of “as expected; as one would expect” in natural Japanese.
さすが先生ですね。 — As expected of a teacher.
かな (kana): I wonder; should I
At its core, かな marks uncertainty the speaker is mulling over:
明日は雨かな。 — I wonder if it’ll rain tomorrow.
かしら (ka shira): I wonder
かしら comes from か (the question particle) plus 知らん, an old form of “I don’t know.” So 来るかしら was originally “Will they come? I don’t know.” That origin explains the meaning: you raise a question and admit you don’t know the answer.
明日は雨かしら。 — I wonder if it’ll rain tomorrow.
かい (kai): yes/no question ending
かい adds a yes/no question to the end of a plain-form sentence, like か does. The difference is tone.
やあ、元気かい？ — Hey there, how are you doing?
じゃないか (janai ka): right; isn’t it
Literally, じゃないか is “isn’t it ~?” In use, the speaker already knows the answer and wants the listener to agree or notice.
あれ、田中じゃないか。久しぶり！ — Hey, it’s Tanaka! Long time no see!
ではないか (dewa nai ka): isn’t it; don’t you think
ではないか has three jobs, and the context tells you which one you are looking at.
なんだ、田中さんではないか。久しぶりだな。 — Well, if it isn’t Tanaka! It’s been ages.
Often confused in this group
- はずだ vs べきだ vs ほうがいい — All three translate as 'should': はずだ is what you expect, べきだ is what's right, ほうがいい is advice. 3時に着くはずだ = it should arrive at 3.
More JLPT N4 grammar groups
- Conditionals and decisions (11)
- Giving, receiving, requests, and keigo (15)
- Passive, causative, and permission (12)
- Te-form helpers for real conversation (15)
- Time, timing, and sequence (17)
- Plans, intention, and change (8)
- Soft examples, lists, and limits (13)
- Hearsay, appearance, and feelings (17)
- Nominalizers, quoting, and comparison (14)