Palestinian amora of the fourth generation; called "the Younger " ("ze'era") to distinguish him from Yannai b. Ishmael. When his father-in-law died Yannai was exempted from the priestly laws of purity in order that he might attend to the interment of the dead (Yer. Ber. 6a; Yer. Naz. 6i). A sentence treating of the importance of an oath and how it is to be made has been preserved in Lev. R. It appears that at Yannai's funeral his pupils did not follow current customs, for which reason they were reproved by R. Mani (Yer. M. Ḳ. 82c).