| Acronym | Definition |
|---|
| J | Just |
| J | Jack |
| J | Java |
| J | Journal |
| J | Japan (soccer league) |
| J | Jet (aircraft type) |
| J | Julia (song) |
| J | Joint (bank account) |
| J | Joint (slang for marijuana) |
| J | Business Class |
| J | Joining |
| J | Junction |
| J | Impulse (physics) |
| J | Juliet |
| J | Jumper |
| J | Joule (unit of energy) |
| J | Jamming |
| J | Jabber (Cisco) |
| J | Postage Due (Scott Catalogue prefix; philately) |
| J | Western Quebec (postal code designation, Canada) |
| J | Out of City (Alabama Public Safety Radio Code) |
| J | Imaginary unit |
| J | Angular Momentum Quantum Number (used in formulae in quantum physics) |
| J | Federal Reserve Bank of Kansas City, Missouri (designates original point of circulation of a dollar bill) |
| J | Jaeger Notation (ophthalmology; size of type used in testing vision) |