| Abbreviation | Definition |
|---|---|
| J | Joule |
| J | Joules |
| J/DEG | Joule Per Degree |
| JD | Julian Date |
| JD | Jupiter Diameter |
| JEZ | Jezebel |
| JFO | John Frederick Oberlin Society |
| JK | Jillion Karat |
| JPD | Jobs Per Day |
| JTU | Jackson Turbidity Unit |
| K | Kelvin |
| k | Kilo (1000) |
| K | Kilobyte (1024 bytes) |
| KA | Kilo Anno |
| KAF | Thousand Acre Feet |
| Kb | Kilobits |
| KB | KiloBytes |
| KB/S | Kilobytes Per Seconds |
| KBIT/S | Kilobits Per Second |
| Kbps | Kilo Bits Per Second |