@manobra

I honnestly did. I took time to read the mecanism and even compare e-currencies. But not enought for sure, I'm probably not a smart guy

Note the transactions I did were amountless, for testing purpose, in order to learn and understand before entering the game, as you advise to do.

Note : As the problem is solved, I changed the topic name consequently

Thank you very much for your quick and precise answer.

Hello.

I'm new to Bc currency manipulations.
 I recently sent .002 bc on an adress (for testing purpose)
From this adress feeded with 0.002 bc,  I took only .001 bc that I sent to another adress feeding an account  I own (for testing purpose again).

Surprise : I perfectly received the 0.001 bc sent on the destination adress, but I only got .0009 bc left on the original adress !!

I used Bitcoin Wallet on Android for these operations (receiving and sending)
 I first suspected a sort of hidden commission (theft ?)  by the programer but when controlling on     https://blockchain.info    the operations, I see no third account involved that could have received the "leaked" 0.0001 bc.
Il only looks as 0.002 - 0.001 = 0.0009 !!

I don't care the 0.0001 leakage of course. But as a first feeling, I have serious doubts on Bitcoin.
Is there any kind of rational explanation  (like fees commission for example) ?

If someone can explain the dumb newbee I am , thanx in advance.