Yes, ADA coin is an altcoin.
Altcoin is a general term for any cryptocurrency that is not Bitcoin. Bitcoin is the first and most well-known cryptocurrency, so it is referred to as the "original coin" or "king coin." All other cryptocurrencies are considered altcoins, regardless of their purpose or underlying technology.
Here are some reasons why ADA coin is considered an altcoin:
It is not Bitcoin: ADA coin is not the first cryptocurrency that was created, and it does not have the same history or community as Bitcoin.
It has its own blockchain: ADA coin has its own blockchain, called Cardano, which is different from the Bitcoin blockchain.
It has its own purpose: ADA coin is designed to be used on the Cardano platform, while Bitcoin is designed to be used as a currency.