13th letter and the 10th consonant , of the English alphabet. The form of the character, like that of the other English letters, is ultimately derived, though with important modifications, from the ancient Phoenician. Its position between L and N is also derived from the ancient Semitic; as in the 119th Psalm, where mem is preceded by lamed and followed by nun. The name mem in Hebrew, like the word mayim, probably signified water, the Ethiopic name of the letter, as well as of water, being mai. The letter M in English has in all positions one uniform, well known sound. It is often called a liquid or semi-vow el, and is a labial nasal, having the same relation to the labial mutes as n to the lingual mutes, and ng to the palatal mutes. The sound of M is one of the easiest to articulate, and is therefore one of the first uttered by children. It is found in nearly all known languages, and in most of them is a prominent letter in the words for mother (mam, mamma), as Sans, mata, Gr. (Dor. ), Lat. mater, Ger. Mutter, Slav, matka, Armen. mair, Heb. em, Chin, mu; for nurse, as Ger. Amine, Slav. mamka; and for breast, as Lat. mamma, Gr. or Armor, mamm. The English sound of M is that which belongs to it also in most of the European languages. In French and Portuguese, however, at the end of a word, and in most cases at the end of a syllable, it loses its sound, and has no other function than to indicate the nasality of the vowel which precedes it. In Latin, m final is the more usual characteristic of the accusative singular. The ancient grammarians ascribed to it in this case a different pronunciation from that which it has elsewhere. The obscurity of this sound, perhaps only indicating the nasality of the vowel, still appears from the fact that in Latin verses m final, followed by a word beginning with a vowel, does not prevent the elision of the preceding vowel. For the most part, the sound of M has come down unchanged from the earliest times. It is in almost every instance an original sound; as for instance, Eng. mete, Anglo-Sax. metan, Mceso-Goth. mitan, Lat. metior, Gr. Sans, ma, Heb. madad, Arab, medda. The following are the principal exceptions, made for euphony: 1. In words of Latin origin, n assimilates itself to a following m, as immense, immerse, commute, for inmense, inmerse, conmute. So in words from Greek, n or a labial sometimes assimilates itself to a following m, as symmetry for synmetry, lemma for lepma; so also d, as ammunition for ad-munition. 2. In words both of Latin and Greek origin, n sometimes conforms itself to a following labial, by becoming m; as imbibe, impend, embark, combine, emblem, symbol, sym-puthy. 3. In words of Teutonic origin, n becomes m before a labial; as Lat. cannabis, Ger. Hanf, Eng. hemp. Where m is now silent, as in the word mnemonics, it once had its appropriate sound. - The Greek and Hebrew M, as a numeral, denoted 40. The Roman M, probably as the initial of mille, denotes 1,000; and this is its numerical value in English.