Aleph or alef has several meanings:

• Aleph (letter) or Alef, the first letter of the Proto-Canaanite alphabet
• Aleph (Hebrew), the first letter of the Hebrew alphabet
• Aleph or Alif (Arabic), the first letter of the Arabic alphabet
• Aleph or Alif (Farsi), the first letter of the Farsi (or Persian) alphabet
• Aleph, a shorthand designation for Codex Sinaiticus, a 4th-century manuscript of the Bible

In science:

• Aleph number or cardinality, a measurement of mathematical sets
  • aleph null ($\backslash aleph\_0$), the cardinality of countable infinite sets
  • aleph one ($\backslash aleph\_1$), the cardinality of certain uncountably infinite sets (if the continuum hypothesis is true, then the set of all real numbers has this cardinality).
• Aleph (inductive logic programming), an advanced system for inductive logic programming
• Aleph (TeX), a stable version of Omega for multilingual typesetting
• ALEPH detector or ALEPH experiment, one of the four detectors of the Large Electron-Positron Collider (LEP) at CERN
• Alef programming language, the concurrent programming language used in early editions of Plan 9
• Aleph kernel was an operating system kernel, notable primarily for being one of the steps in the evolution of the Mach kernel
• Aleph, an integrated library system from Ex Libris LTD used to manage library operations

In popular culture:

• Aleph (book), a short story by author Georg Brandes
• "The Aleph", a short story by Argentine author Jorge Luis Borges
• Aleph (Buddhist group), a religious sect in Japan formerly known as Aum Shinrikyo
• Aleph Zadik Aleph, the men's order of the B'nai B'rith Youth Organization (BBYO), an international youth-led high school fraternity for Jewish teens. Aleph can also refer to a member of this group.
• Aleph One (computer game), an ongoing project related to the computer game series Marathon
• Mount Aleph, an important location in the video game Golden Sun
• Alef, one of the main protagonists in the SEGA video game Shining Force
• Aleph, the real name of the protagonist in the video game Shin Megami Tensei II
• Aleph, a character in the comic book series Global Frequency, written by Warren Ellis

알레프 | アレフ