etf vs mutual fund liquidity

which is more liquid?

the book says etf has more liquidity but also says the disadvantage of etf is risk of illiquidity when you need to sell.

ETF’s are more liquid.

ETF’s can be bought and sold throughout the day at the prevailing bid/ask. But there may be insufficient liquidly at any given time in the market. This generally isn’t the case unless you’re trading a specialized ETF with thin trading volume.

Mutual funds can only be bought/sold at NAV, which is calculated using end of day prices.