A letter which performs the function of a diacritical mark; (specifically in Hebrew writing) a consonantal sign which indicates that a vowel sound is to be supplied.
mater lectionis/ˌmeɪtə lɛktɪˈəʊnɪs/ /ˌmɑːtə lɛktɪˈəʊnɪs/
Mid 17th century; earliest use found in Brian Walton (1600–1661), bishop of Chester and biblicist. From post-classical Latin mater lectionis from classical Latin māter + lectiōnis, genitive singular of lectiō reading, probably after post-biblical Hebrew 'ēm qĕrī'āh (also 'ēm haqqĕrī'āh), lit. ‘mother of the reading’.