Liquidity
Plain English
How easily you can buy or sell an asset without significantly changing its price. High liquidity = lots of buyers and sellers, easy to trade. Low liquidity = few traders, your orders impact price heavily. Like selling a popular product (liquid) vs a rare antique (illiquid).
Technical
Measure of market depth and ability to execute large orders without substantial price impact. Quantified by: order book depth, bid-ask spread, volume, TVL in liquidity pools. Fragmented liquidity across DEXs/CEXs affects execution quality. Solana aggregators (Jupiter) route orders across venues for optimal liquidity. Illiquid markets vulnerable to manipulation and high slippage.