Mater lectionis
A mater lectionis ( MAY-tər LEK-tee-OH-niss, MAH-tər -; Latin for 'mother of reading', pl. matres lectionis MAH-trayss -; original Hebrew: אֵם קְרִיאָה, romanized: ʾēm qərîʾāh) is any consonant letter that is used to indicate a vowel, primarily in the writing of Semitic languages such as Arabic, Hebrew and Syriac.