• Safety Equipment Institute, a private, non-profit organization established to test safety and protective products
• Scuba Educators International, a non-profit diver training organization
• Seebeck effect imaging, uses a laser to generate thermal gradients in conductors in order to locate electrically floating conductors
• Service endpoint interface, a term used in Java Platform, Enterprise Edition when exposing Enterprise JavaBean as web service
• Slough Estates International, the former name for SEGRO
• Software Engineering Institute, a federally funded research and development center at Carnegie Mellon University
• Space Exploration Initiative, a plan envisioned by former U.S. President George H.W. Bush with manned Moon and Mars missions
• SpaceWorks Enterprises, Inc., a small aerospace engineering company in the United States
• Stockholm Environment Institute, a non-profit institute that specializes in sustainable development and environmental issues
• Solid Electrolyte Interphase of lithium-ion batteries
• SUNY Eye Institute, a medical and basic sciences research institute in New York
• Sustainable Ecosystems Institute, a non-profit organization dedicated to science for society
• Systems Evolution Incorporated, a niche, mid-size consulting company based out of Mason, Ohio.

• Sei whale
• Sei Ashina, an actress
• Seri language, sei is the ISO 639-code of that language
• 6 (number), sei is the Italian word for six
• Endpoint interface, service endpoint interface
• Indrek Sei (born 1972), Estonian freestyle swimmer

• Software Engineering Institute, ein Forschungs- und Entwicklungszentrum in den Vereinigten Staaten von Amerika
• Solid electrolyte interphase, siehe Lithium-Titanat-Akkumulator

• Stockholm Environment Institute
• Software Engineering Institute, ett institut för programutvecklingsmetodik vid Carnegie Mellon University
• socioekonomisk indelning, ett system som används vid statisktiska undersökningar, bland annat av SCB (Statistiska centralbyrån) för att definiera socialgruppstillhörighet

Mena omdirigerar hit. För förkortningen, se MENA.

SEI wypełnia swoje zadania w dwóch obszarach: Software Engineering Management Practices i Software Engineering Technical Practices. Pierwszy dotyczy udoskonalania procesów zarządzania rozwojem i implementacją oprogramowania, drugi – ulepszaniem technicznych metod i narzędzi rozwoju oprogramowania; celem nadrzędnym jest naukowe opracowanie organizacyjnych i technicznych ram rozwoju software'u, które zastąpią doraźne i niezorganizowane metody jego tworzenia.

• Società Editrice Internazionale - casa editrice italiana
• Software Engineering Institute