Bitcoin Forum

I am very new to bitcoins. I

 have one question. Suppose some one copied their private key and saved it in their harddisk.

Next they will do the transaction. Now since you already copied the private keys can you use it again?

How bitcoin prevent this? 

Thanks in advance for clearing my doubt.

You can use the private key for the same wallet. The private key does not change with every transaction. It is permanent and stable. If you want a new private key, then you need to create a new Bitcoin wallet.

Ok got it. It was my mistake. I thought coins are stored in your computer with every bitcoin as its own address. Now I understand it perfectly. private key is only for wallet address. Not for bitcoin

Your terminology is wrong.

A "wallet" is a container that holds one or more "private keys" (and the associated "addresses"). A "wallet" is not a "private key" or an "address".

If you want a new address, the wallet will create one for you by generating a new private key. Most wallets do that automatically every time you use an address.

Typically, a wallet has a unique "seed" or "recovery phrase", and if you want a new wallet, you get a new seed.

People write things like "send bitcoins to a wallet" or "a wallet has X bitcoins" for convenience when they actually mean "send bitcoins to an address in a wallet" or "a wallet has addresses with a total of X bitcoins"