售 is a bound form (b.f.), meaning it cannot stand alone as an independent word. It carries the core meaning of 'sell' and is used as a morpheme in compounds like 销售 (xiāoshòu, to sell), 售票 (shòupiào, ticket selling), and 出售 (chūshòu, to sell/be on sale). You'll never see 售 used as a standalone verb — always look for it in multi-character words.