とは限らないnot always; not necessarily
Something people take for granted has exceptions: expensive isn't always good. You grant that it is often true and hold back the "always".
Expensive products don't always last long.
A free service is not necessarily a good deal.
How to form it
Plain form + とは限らない
A noun or a な-adjective can keep だ or drop it: 得（だ）とは限らない. Politely, とは限りません.
- Before it
- A rule or a guess that sounds safe: expensive means good, the forecast is right.
- Often with
- 必ずしも (not necessarily), いつも (not always), みんな or だれでも (not everyone) in front.
- Tone
- Level-headed. It corrects an assumption without calling it wrong.
- Where you'll meet it
- Everywhere: conversation, advice, essays, the news.
In use
Hard work doesn't always pay off.
A quiet place isn't necessarily easy to concentrate in.
必ずしも announces the ending: a "not necessarily" is on its way.
Just because a restaurant is famous doesn't mean the food is good.
からといって, "just because", often sets it up.
The forecast says sunny, so we won't need umbrellas.
Not necessarily. The weather in the mountains changes quickly.
そうとは限らない is a reply in itself: "not necessarily".
Two things to know
A rule or a guess, not a fact you know
とは限らない needs something nobody can be sure of: a rule over many cases, or a guess about one. English says "not necessarily" about a fact you know too, such as your own taste. There Japanese says わけではない.
Not all non-drinkers dislike alcohol.
A rule about people in general. It has exceptions.
I don't drink, but it's not that I dislike alcohol.
One person, and you know the answer.
Not said: 私は
(I don't drink, but I don't necessarily dislike alcohol.)
Your own taste is neither a rule nor a guess.
After a negative: it could happen
With a negative in front it is a warning: you think it won't happen, but it might. It comes close to かもしれない.
Even if you prepare thoroughly, there's no guarantee you won't fail.
Close neighbours
わけではないN3
"It's not that…": you take back a conclusion the other person might jump to. Often it means "not entirely".
I chose the online course, but that does not mean I dislike learning in a classroom.
Rejects a rule for being too simple: one thing alone doesn't settle it.
Simply adding more videos does not make a course good.
Check yourself
1What does this mean?
高い
Choose an answer to see why.
2Which one fits?
私は
Choose an answer to see why.
3What does this mean?
明日、
Choose an answer to see why.
More sentences
A famous person is not necessarily an expert in that field.
Not all young people know a lot about new technology.
Not everyone can use it right away just by reading the instructions.
However accurate it is, there's no guarantee the weather forecast won't be wrong.