י Yod, the tenth letter of the Alphabet. It interchanges with ו, e.g. יָדַע a. וַדַּאי; with א as יבד a. אבד; with ה, v. letter ה.—י is frequently a mater lectionis for ē, ĕ, and ī, ĭ, e.g. לֵילֵךְ, לֵישֵׁב (for b. h. לָלֶכֶת, לָשֶׁבֶת); הֶיסֵּב = הֶסֵּיב, דִּיבּוּר = דִּבּוּר.—יי is frequently used to indicate the consonantal value of י, as הִתְיָירֵא = הִתְיָרֵא.