 The Talmud and the rabbis explain the variations in "plene" and "defective scriptum" found in the Torah as being merely a "Halacha le-Moshe mi-Sinai" (a Law given to Moses at Sinai).In the Semitic languages (Hebrew, Aramaic and Arabic), paleographers often describe the addition of a "plene" consonantal letter, such as ""waw"" and ""yod"" (used in place of the vowels "o", "u", "i", and "ei"), as employing "matres lectionis" in its reading, although not all "plene" letters used in Hebrew words are indeed a "matres lectionis".The ethnographer, Jacob Saphir (1822–1886), in his 19th-century work "Iben Safir", mentions the tradition of orthography found in the "Halleli Codex" of the Pentateuch, in which he laid down the most outstanding examples of "plene" and "defective scriptum" copied generation after generation by the scribes.