What is the name of the original and most widely used Bitcoin client?

What is the name of the original and most widely used Bitcoin client? Bitcoin Core is the original Bitcoin client’s modern name and the network’s reference implementation.

Satoshi Nakamoto released the first open-source Bitcoin client in January 2009. It was initially called simply Bitcoin, and later versions became known as Bitcoin-Qt. After version 0.9, the software was renamed Bitcoin Core to distinguish the client from the Bitcoin network itself.

Bitcoin Core functions as full-node software: it downloads and validates the blockchain, checks transactions and blocks, and connects to other nodes. It also includes wallet functionality, although many users now use separate wallet applications rather than storing funds in a full node.

“Bitcoin Core” can be confused with a lightweight wallet such as Electrum. Electrum does not independently download and validate the entire blockchain in the same way. Bitcoin Core is also not the blockchain itself; it is a major software implementation used to participate in the peer-to-peer Bitcoin network.