| Acronym | Definition |
|---|
| NEI | Nuclear Energy Institute |
| NEI | National Eye Institute (NIH) |
| NEI | Not Enough Items (gaming) |
| NEI | National Emission Inventory |
| NEI | Nova Economia Institucional (Portuguese: New Institutional Economics; Brazil) |
| NEI | Network Entity Identifier |
| NEI | Network Element Interface |
| NEI | North Eastern India |
| NEI | Neuroendocrine-Immune |
| NEI | Netherlands East Indies |
| NEI | Not Elsewhere Included |
| NEI | Nederlands Economisch Instituut (Dutch: Netherlands Economic Institute) |
| NEI | Neutrophil Elastase Inhibitor |
| NEI | National Education Institute (Slovenia) |
| NEI | Not Enough Information |
| NEI | Network Engineering, Inc. (Indianapolis, IN) |
| NEI | Nuevos Estados Independientes (Spanish: Newly Independent States) |
| NEI | New England Independent (est. 2002; wrestling) |
| NEI | Northwest Earth Institute (Portland, OR) |
| NEI | National Executive Institute (FBI Academy) |
| NEI | Nippon Electric Instrument, Inc. (Japan) |
| NEI | Network Enterprises, Inc. (various locations) |
| NEI | New Economy Index |
| NEI | National Elevator Industry |
| NEI | Noise Equivalent Irradiance |
| NEI | Nevada Early Intervention |
| NEI | Nuclear Energy International |
| NEI | New England Interactive |
| NEI | Non Explosive Initiator |
| NEI | Nucleo de Estudantes de Informatica |
| NEI | National Expertise Index (Canada) |
| NEI | Núcleo de Estudantes de Informática (Portuguese: Informatics Students Association) |
| NEI | Network Equipment Identifier |
| NEI | Nonprofit Education Initiative |
| NEI | New Equipment Introduction |
| NEI | New Employee Information |
| NEI | Network Engines Incorporated |
| NEI | Network Elements Incorporated |
| NEI | Network Element Integration |