Hauv kev ua lej, muaj lub tswv yim ntawm "set", nrog rau cov piv txwv ntawm kev sib piv cov teeb tsa tib yam nrog ib leeg. Cov npe ntawm hom kev sib piv ntawm cov txheej txheem yog cov lus hauv qab no: bijection, txhaj, surjection. Txhua tus ntawm lawv tau piav qhia ntau yam hauv qab no