What exactly is the definition of a Bitcoin node? This page claims there are about 11k nodes in the Bitcoin network. I wonder what exactly constitutes a "node" in the network. For example, if I connect to the network and do nothing, am I still considered in this 11k figure? Or do I have to have an "effect" on the network in some ways, e.g., broadcasting empty blocks or trying to mine honestly.
Another question is do mining pools, as a whole, count only as a single node in the network?

In general, what's the precise definition of a node in the context of Bitcoin network ?
A node is a computer that has a copy of the blockchain (or at least a part of it), and broadcasts and receives transactions and blocks from other nodes according to the bitcoin protocol.

The blockchain is more than 100GB, so most people use a lightweight client that connects to a service that connects to a node on the network. Clients are not considered nodes on the network.

A couple of specific examples of each type:


Bitcoin Core or Armory run full nodes on the network.
Mycelium or the Trezor Wallet are clients that connect to a server, not directly to the bitcoin network, and aren't included in the count.


The computers in a mining pool do not need to connect to the network so do not count as nodes (they are only solving a cryptographic problem and don't care about the transaction data). The mining pool will have at least one node that connects to the network to download and broadcast the transaction data, so the number of nodes in a pool depends on how many the maintainers of a specific pool decide to activate.