| Abbreviation | Definition |
|---|---|
| JET | Joint European Torus |
| JMP | Journal of Mathematical Physics |
| JMPC | Journal of Materials Physics and Chemistry |
| JND | just noticeable difference |
| JOPA | Journal Of Physics A |
| JOPG | Journal of Physics G |
| JPAC | Joint Physics Analysis Center |
| JPARC | Japan Proton Accelerator Research Complex |
| JPCS | Journal of Physics Conference Series |
| JPG | Journal of Physics G |
| JPP | Journal of Plasma Physics |
| JSN | Japanese Singularities Network |
| JT | Joule-Thompson effect |
| JTAP | Journal of Theoretical and Applied Physics |
| JTPC | Journal of Theoretical Physics and Cryptography |
| JULIA | Jena University Laboratory of Ion Acceleration |
| JULIE | Joint Utilization of Laser Integrated Experiments |
| K | Boltzmann Constant |
| KAC | Kinetic Armor Class |
| KANUPP | Karachi Nuclear Power Plant |