Mim is the thirteenth letter of the Syriac abjad, with the numeral value forty. It writes m, a voiced bilabial nasal. It joins on both sides, so it carries a connected run onward rather than breaking it.
Its name is the inherited Northwest Semitic word for water. The same name and the same place in the sequence are held by Hebrew mem and, through the Phoenician sequence the Greeks borrowed, by the Greek mu, which is one of the plainest illustrations of how far a single letter of one alphabet can be traced.
Syriac has no set of final letters of the kind Hebrew developed. A Hebrew mem written at the end of a word is a different character with a different shape and, in the numeral system, a different value. A Syriac mim at the end of a word is the same letter drawn as the last member of a connected run. The distinction sounds technical and it matters for counting: Hebrew is often described as having twenty-two letters and five finals, while Syriac is described as having twenty-two letters, full stop, with positional forms that belong to the letters rather than standing beside them.
Mim is also frequent at the head of Syriac words, since m is the prefix of a large class of nouns and of participles, so it is a letter a reader meets in every position.