E/I, a type of children's television programming shown in the United States
Ei (album), an album by Maija Vilkkumaa
"Ei" (song), its first single
Eerie, Indiana, an American television series
Enrique Iglesias, Spanish pop music singer-songwriter
Exposure index, the film speed rating of photographic film as exposed
Businesses and organizations
Aer Lingus (IATA code EI), the flag airline of Ireland
The Earth Institute, a collection of research centers at Columbia University
Education International, a global union federation of teachers' trade unions
Elektronska Industrija Niš, electronics enterprise based in Niš, Serbia
Energy Institute, the main professional organization for the energy industry within the UK
Engineers Ireland, the professional body for engineers and engineering in Ireland
Enterprise Ireland, is the Irish government organisation responsible for the development and growth of Irish enterprises in world markets.
Expeditors International, the global logistics and freight forwarding company based out of Seattle, Washington
The Electronic Intifada, an online publication covering the Israeli-Palestinian conflict from a Palestinian perspective
Linguistics
⟨ei⟩, a digraph found in some Latin alphabets
The original name of the Greek letter Epsilon
ɛɪ in the International Phonetic Alphabet (IPA)
Places
Ei, Kagoshima, a town located in Ibusuki District, Kagoshima, Japan
Emerald Isle, North Carolina, a town in Carteret County, North Carolina, United States
Science, technology, and mathematics
Ei (prefix symbol), the prefix abbreviation of the binary unit prefix "exbi"
Earth Interactions, a scientific journal published by the American Meteorological Society, American Geophysical Union, and Association of American Geographers
Ei Compendex, an engineering bibliographic database
Electron ionization, an ionization method in which energetic electrons interact with gas phase atoms or molecules to produce ions
Electronic ignition, a variety of modern ignition system
Engineering Index, an article index for engineering journals
Engineer intern, an intermediary step to becoming a Professional Engineer
Environmental illness (multiple chemical sensitivity), a chronic medical condition characterized by symptoms that the affected person attributes to exposure to low levels of chemicals
Ionization energy (EI), the energy required to remove one electron from one atom to another
Equine influenza, the disease caused by strains of Influenza A that are enzootic in horse species
Exponential integral, a special function defined on the complex plane given the symbol Ei
Other uses
Education Index, a United Nations measure of the level of educational development in a country
Emotional intelligence, the ability to identify, assess, and control emotions
Employment insurance, the unemployment benefits system of Canada
Encyclopaedia of Islam, an encyclopaedia of the academic discipline of Islamic studies
Enhanced interrogation, a euphemism for torture
Ex infra, a Latin phrase meaning 'from below'
Extreme ironing, an extreme sport and a performance art
Esercito Italiano, Italian language for Italian Army
Raiden Shogun, real name Raiden Ei, a playable character from Genshin Impact