Basic stem derivation

Hello, everybody!

I'd have a question if I may: what is the proper method of determining the basic stem of a verb?
I have read that we should take 1) the infinitive form minus the infinitive ending (mostly ть), and 2) the 3rd person plural form minus its ending; and afterwards the longer one is the basic stem. (And if they are of the same length, the 2) is the basic stem.)
But what is then the case with the verb "спать", the 3rd person plural of which is "спят", and using the algorithm above the basic stem would be "спй".
And one more question about this topic: what is the rule for forming the infinitive form from the basic stem? I thought at first that we simply should add the ending (mostly -ть) to the stem (and of course taking care of the truncation if needed), but what is then the case with the verb "гнать", the 3rd person plural of which is "гонят"?

Thank you very much for your answers in advance.

Steve

Quote:

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Originally Posted by szaboistvan

Hello, everybody!

But what is then the case with the verb "спать", the 3rd person plural of which is "спят", and using the algorithm above the basic stem would be "сп [s:2k0eshj9]й[/s:2k0eshj9]".
And one more question about this topic: what is the rule for forming the infinitive form from the basic stem? I thought at first that we simply should add the ending (mostly -ть) to the stem (and of course taking care of the truncation if needed), but what is then the case with the verb "гнать", the 3rd person plural of which is "гонят"?

Thank you very much for your answers in advance.

Steve

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спать
Я сплю спал/спала
Он/она спит спал/спала
Мы спим спали
Вы спите
Они спят спали

Гнать
Я гоню гнал
Он/она гонит гнал/гнала
Мы гоним гнали
Вы гоните гнали
Они гонят гнали

What do you need these stems for? If you are a beginner, my advice: forget it for now.
Anyway, you can take a look here:
http://www.alphadictionary.com/rusgrammar/verb.html
http://www.seelrc.org:8080/grammar/main ... nguageID=6
http://www.ielanguages.com/russian.html

Lampada, thanks for the reply, your correction about the я being the ending instead of "а" gave the answer to my first question.
About the infinitive formation: it is more complex than I thought at first, though I found a very good description of it in a book written by Alexander Lipson (Title: A Russian Course).

Steve