Script

• Em or M, the thirteenth letter of the Roman alphabet

Computing

• End of Medium, an ISO C0 control code
• emphasis (typography), or , the HTML element for emphasis
• Expectation-maximization algorithm, used for statistical computing

Scientific

• Effective microorganisms or EM-Technology by Dr. Teruo Higa
• Electromagnetic
• Electromagnetism (diamagnetism) as compared to ferromagnetism (paramagnetism)
• Electromigration - A common issue encountered in integrated circuit design
• Electron microscope
• Electron multiplier
• Exametre (symbol Em), an SI unit of length (equal to 10¹⁸ metres)

Medicine

• Erythema multiforme
• Emergency medicine

Typography & orthography

• em (typography), a unit of measure used in orthography, typography, and also Cascading Style Sheets (CSS). The em space is one em wide.
• The em dash (—), which is one em wide.
• Em (Cyrillic), A phoneme of the Cyrillic alphabet. It corresponds directly to the Latin alphabet letter 'M' and is pronounced similarly.
• The pronunciation, in English, of the letter M.

Social

• An enlisted Man of the United States Army.
• One of the Spivak pronouns.
• EM, Reuters Instrument Code for the 1-month LIBOR futures contracts at the Chicago Mercantile Exchange.
• The common short form of some given names, e.g. 'Emma', 'Emily', 'Emmett', 'Emmanuel', and 'Emerson'.
• Common abbreviation for electronic music.
• Common abbreviation for emerging markets.

Music

• EM and Em are abbreviations for the E Major and E Minor chords, respectively.
• Electronic music
• E minor scale
• Eminem, a rapper
• Extraordinary Machine, a Fiona Apple album

Other

• The European Movement
• The Erasmus Mundus Programme
• The IATA code for Aero Benin
• The IATA code for Empire Airlines
• Emergency management
• Extreme Makeover
• The model railway EM gauge (Eighteen Millimetres)
• NZR EM class series of Electric Multiple Units purchased by the New Zealand Railways Department.