tanhqlさん、こんにちは。
tanhql said:
1) how do you use 唯 to mean 'only'?
林檎を唯一個?唯林檎を一個?林檎唯を一個?
and when apple is not the topic, do you say:
唯一個の林檎?
There are several ways to express "only";
ただ(唯、只)
唯一
たった
~だけ
etc.
ただ is normally written in hiragana.
林檎をただ一個
is correct. You can also say
ただ一個の林檎を.
As far as "only" modify "one" (not apple), it should be always placed in front of "one" (一個).
Alternative expressions are
林檎をたった一個、林檎をただひとつ、林檎をたったひとつ、林檎をひとつだけ
たったひとつの林檎を、ただひとつの林檎を、たった一個の林檎を、
just for example.
tanhql said:
2) how do you use だけ to mean 'just'? as in それはだけではありません. does だけ have to be used with では? what are the positive/negative and formal/informal forms of だけではありません? is だけではない the informal negative form?
No, だけ can be used on its own.
e.g.
林檎をひとつだけ食べました。
それだけではありません
means "not only that (but...)"
Yes,
それだけだ positive
それだけではない negative
それだけです positive (polite)
それだけではありません negative (polite)
tanhql said:
3) can ~くん be used for female names?
Yes, but only in a specific situation.
Sometimes a big boss calls employees with ~君(くん).
Then he can call a female employee ~君, too.
But it sounds rather arrogant (though it depends on how important he is), and the female might get offended (again it depends on the situation).
tanhql said:
4) should it be 俺に見える? or 俺を見える?as i've heard the formal spoken on a japanese show. the translation is 'you can see me?'.
Can you see me? is
俺が見える?
見える is intransive verb, it is more closer to "appear" or "show (oneself)" than "see".
俺に見える?
means "Can I see (something/someone)?"
俺を見える
is ungrammatical.
tanhql said:
5) i know that negative ~下さい forms is formed by informal negative+で下さい, like 行かないで下さい. what about ~なさい forms? 待ちなさい is 'wait!' in command form. what is the negative form of it?
行く
行きなさい positive
行かないでください negative
待つ
待ちなさい positive
待たないでください negative
tanhql said:
6) how do you use たくさん and 少し in sentences to express amount? and does たくさん have a kanji counterpart?
少しの/たくさんの林檎
少しの/たくさんの水
林檎を少し/たくさん買った
水を少し/たくさん飲んだ
Kanji for たくさん is 沢山.