Option expiries in Bitcoin and Ether refer to the predetermined dates when options contracts for these cryptocurrencies expire. On these dates, the options holders must decide whether to exercise their right to buy or sell the underlying asset at the agreed-upon strike price. The expiration of these options can lead to significant market movements as traders adjust their positions, potentially impacting the price of Bitcoin and Ether. These expiries are crucial for traders and investors as they can influence market volatility and liquidity.