分からない／分かりません ＡＮＤ する／します

[kisu]

Okay... so what is the difference in 分からない and 分かりません..? As far as I know they mean the same thing.. so which would you use and when?

Same goes for する and します (the verb forms.. normal and the -ます) Which/when...?

Help? ^^

~Kisu

[okaeri_man]

welcome to the world of plain form. they mean the same thing, but 分かりません is more formal than 分からない . every verb has a plain form. actually, i like to think of it as every verb has a polite form (ie する is the verb, します comes from it).

a good textbook or internet site could explain the situations and how they are used grammatically. essentially you use plain form when talking to friends, talking to your family, talking to yourself, and talking to anyone who's at the same or lower rank of you socially (such as a boss talking to his employee).

[Scrivener]

Like okaeri_man said so well, it's to do with formality and politeness. Always use "-masu" & "desu" unless you are with good friends (or the other examples above).

I'll just give some unsolicited advice as usual. Learning how to use the right "politeness level" in Japanese can seem like a hassle when you start. Why bother learning two forms for every verb? HOWEVER:
(1) It follows fairly simple rules, so it's not too hard to learn
(2) Once you get the hang of it, it makes Japanese much more FUN than other languages, because you can play around with it
(3) If you can speak at the right politeness level, you will get on much better in Japanese society - especially the world of employment.

Especially if you are a young woman, and if you are dealing with older men, you need to make a big effort to use the right politeness level (basically, be as polite as possible without going over the top). Japanese people will be more impressed with you, and they are more likely to trust you and accept you.

[kisu]

Good to know, thanks much ^^

~Kisu

[Mike Cash]

The plain form is also used internally in sentences to modify following elements. Fills sort of the same function as relative pronouns and their clauses in English.