From The Leningrad Codex: A Facsimile Edition (Eerdmans/Brill)

LENINGRAD CODEX. A leaf from the Leningrad Codex, the oldest complete Hebrew Bible (tenth century) contains notes in the top, bottom and columnar margins of the text. In an effort to preserve the best possible text, scribes noted important information such as word misspellings, word meanings or the number of times a word appeared in the text. Brief jottings are called Masorah parva (Mp). Longer explanations are called Masorah magna (Mm).