What is the difference between an altcoin and a cryptocurrency?

The terms "altcoin" and "cryptocurrency" are often used interchangeably, but they have distinct meanings that reflect their roles within the broader digital currency ecosystem:

1. **Cryptocurrency**:
   - **Definition**: Cryptocurrency is a general term that refers to any digital or virtual currency that uses cryptography for security and operates on a decentralized network (usually a blockchain).
   - **Characteristics**: Cryptocurrencies are typically decentralized, meaning they operate without a central authority like a government or financial institution. They use cryptographic techniques to secure transactions, control the creation of new units, and verify the transfer of assets.
   - **Examples**: Bitcoin (BTC), Ethereum (ETH), Litecoin (LTC), and many others are considered cryptocurrencies because they fulfill the criteria of using cryptography, decentralized networks, and digital transactions.

2. **Altcoin (Alternative Coin)**:
   - **Definition**: Altcoin is a term that specifically refers to any cryptocurrency other than Bitcoin. It was originally coined to differentiate newer cryptocurrencies that emerged as alternatives to Bitcoin, offering different features or improvements.
   - **Characteristics**: Altcoins may share similarities with Bitcoin in terms of technology (blockchain, cryptography) but often introduce variations or enhancements. These could include different consensus mechanisms (Proof-of-Stake, Proof-of-Authority), alternative use cases (smart contracts, privacy features), or different economic models (tokenomics).
   - **Examples**: Ethereum (ETH), Ripple (XRP), Litecoin (LTC), and thousands of other cryptocurrencies are considered altcoins because they are alternatives to Bitcoin and offer unique features or functionalities.

**Key Differences**:

- **Scope**: Cryptocurrency is a broad term encompassing all digital currencies that use cryptography for security and operate on decentralized networks. Altcoin specifically refers to cryptocurrencies that are alternatives to Bitcoin.
 
- **Origin**: Altcoin originated as a term to categorize cryptocurrencies that followed Bitcoin's creation, offering different approaches or improvements. Cryptocurrency is a more general term without specific historical connotations.

- **Variety**: There are thousands of cryptocurrencies, with Bitcoin being the first and most well-known. Altcoins make up the majority of these, each with its own unique features, purposes, and communities.

In summary, while all altcoins are cryptocurrencies, not all cryptocurrencies are altcoins. Altcoins specifically denote alternative digital currencies to Bitcoin, whereas cryptocurrency encompasses a broader category of digital currencies that share cryptographic principles and decentralized operation.