Samekh

Samekh or Simketh is the fifteenth letter in many Semitic alphabets, including Phoenician, Hebrew, and Aramaic, representing .
The Phoenician letter is where the Greek Xi (Ξ, ξ) comes from.
Hebrew Samekh.
Samekh represents , a voiceless alveolar fricative. Unlike most Semitic consonants, the pronunciation of remains constant between vowels and before voiced consonants.
Samekh in gematria has the value 60.
Samekh and Mem form the abbreviation for the Angel of Death, whose name in Hebrew is "Samael". It also stands for centimetre.