Synonyms?

[david-us.livejournal.com]

I was wondering if some of you native Russian speakers could tell me if the following word pairs are completely synonomous in that any sentence construction where one is used could just as easily be used by creating a sentence using the other word - without changing the context. If the context changes, could you briefly explain in what way the words are different by creating your own example sentences highlighting this difference?

The reason I ask this: For some reason, when I attempt to speak Russian I have a strong preference for the first word in each pair. Yet, when I listen to native Russians speak (online Russian radio) I frequently hear usage of the other word.

здесь - тут  (This is the least perplexing for me as I actually do hear many native Russian speakers use здесь. The problem is that I don't think I would ever use "тут" in any other context except for an exchange where the word "там" is used. "Где Иван? Он там?"  "Нет. Он тут!" For some reason, my usage of "тут" is completely limited to that type of exchange.)

теперь - сейчас

нельзя - невозможно (I find it interesting how Russians will often create an adverb by simply negating its antonym: немедленно, for example. That is very counter intuitive to English speakers. If we mean "quickly" we don't think "not slowly". I would probably always use быстро where some may use немедленно.)

можно - возможно

учиться - заниматься

If you can think of any additional word pairs for which English speakers typically have a preference for the wrong one, I'd be interested in reading about it.

Thanks!

David Emerling
Memphis, TN