| C3S | Command, Control, and Communications Systems |
| c3s | Command, Control, and Computer Systems |
| C3SMP | Command, Control, and Communications Systems Master Plan |
| C4 | Command, Control, Communications, and Computers |
| C-4 | Composition C-4 plastic explosive |
| C4CM | Command, Control, Communications, and Computer Counter-Measures |
| C4I | Command, Control, Communications, Computers, and Intelligence |
| C4IFTW | Command, Control, Communications, Computers, and Intelligence For The Warrior |
| C4IM | Command, Control, Communications, Computers, and Information Management |
| C4IP2 | Command, Control, Communications, Computers, and Intelligence Power Projection |
| C4IR | Command Control Communication Computers Intelligence And Recognition |
| C4ISR | Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaisance |
| C4ISTAR | Command, Control, Communications, Computers, Intelligence, Surveillance, Target Acquisition, Reconnaissance |
| C4ME | Command, Control, Communications, and Computers Mission Environment |
| C4S | Command, Control, Communications, and Computer Systems |
| C5 | Command, Control, Communications, Computers, and Counter-intelligence |
| C-5 | Cargo aircraft model 5 (Galaxy) |
| CA | Can't Add |
| CA | Chaplain Assistant |
| CA | Civil Administration |