"Have to" in Japanese

[stormyf5]

I've been a Japanese student for several years and I'm still having issues with all the different ways
there are to say "must" in Japanese. There's the ないと form the しなければならない form and another
casual form I'm not ever sure how to type in Hiragana.

Could the community outline when the different forms are to be used, what the nuances are, and add any I
might have missed?

Thanks!

[community.japanese]

stormyf5-san,
Good question!
～しなければ　ならない is the most common way to say "must (do something)".
～しないと is rather casual and it's actually short version of ～しないと　いけない (which is already a bit casual
than ～しないければ・・・）
I can even say that ～しなければ　ならない is quite useful since it can be used in both casual and formal situations.
～しなければ　なりません --- most formal
～しなければ　ならない --- less formal

Hope this helps!

Natsuko(奈津子),
Team JapanesePod101.com