Only in the sense that it uses a blockchain, which Bitcoin pioneered. Ethereum has a separate blockchain that has several significant technical differences from Bitcoin’s blockchain. See this Ethereum StackExchange answer for a detailed explanation.
Ether, the currency used to complete transactions on the Ethereum network (learn more) and Bitcoin have many fundamental similarities. They are both cryptocurrencies that are rooted in blockchain technology.
While it's commonly believed that the price of ETH follows Bitcoin, research shows that ETH is an independent asset. ... However, if analyzing on a wider time frame, it turns out that the prices of most cryptocurrencies — especially of Ether (ETH) — could mostly depend on the valuation of Bitcoin (BTC).