かもしれないmight; maybe
かもしれない is "might" or "maybe": something is possible, but you wouldn't bet on it. With friends it shrinks to かも.
There may still be some tickets left.
How to form it
Plain form + かもしれない
行くかもしれない, 高いかもしれない. A noun or a な-adjective drops だ: 雨かもしれない, 静かかもしれない (but 雨だったかもしれない). Sometimes written かも知れない.
Polite
Plain form + かもしれません
The word before it stays plain: 行くかもしれません.
With friends
Plain form + かも
Possible, and no more than that
You can't say yes and you can't say no. もしかしたら, "possibly", often goes with it. It works for your own plans too, when nothing is decided.
The schedule may change next week.
Maybe we've taken the wrong road.
I might go to Hokkaido during summer vacation.
"Might have" and "might not"
English changes "might". Japanese changes the word before かもしれない.
Yamada may have left ahead of us.
The email may not have arrived.
"Maybe" is not たぶん
English speakers reach for たぶん to say "maybe". たぶん is "probably": you think it likely. When it could go either way, it is かもしれない.
I'll probably go to tomorrow's party.
The host can expect you.
I might go to tomorrow's party.
The host can't count on you.
Softening what you say
People also say it when they are fairly sure, so as not to sound too sure: to disagree gently, to give advice, to warn of bad news.
That may be so, but I like this one better.
It might be better to go home early today.
Sorry, I might be a little late.
かも
そうかも is "could be" or "you might be right".
Isn't this the wrong road?
You might be right.
I might have left my keys at home.
Close neighbours
でしょう・だろうN5
"Probably": you think it likely. It isn't used for your own plans; かもしれない is.
Tomorrow it will probably start raining in the afternoon.
と思うN4
"I think": you put it forward as your opinion or your guess.
I think the trains will be crowded tomorrow.
はずだN4
"Should": you have a schedule, a promise or a fact to go on.
According to the schedule, the train should arrive at ten.
"There is a possibility": it sounds worked out from the facts, where かもしれない is your own guess. It can also say how likely: 可能性が高い, "likely".
I'm sorry, there is a chance I will be a little late.
A message at work: it reads as an estimate.
おそれがあるN2
"There is a risk that": the wording of warnings and the news, for bad things only.
Heavy snow may delay deliveries.
Check yourself
1Which one is right?
Choose an answer to see why.
2Two friends answer your invitation. Which reply means you should expect them?
Choose an answer to see why.
3What does this mean?
彼は
Choose an answer to see why.
More sentences
The flight may be canceled because of the typhoon.
He may not know the circumstances.
This area might be quiet at night.
A seat may become available tomorrow.
This problem may be harder than expected.
There may be an error in this calculation.