HA
- ha – (s) Hausa language (ISO 639-1 code) – Hectare
- HA – (s) Haiti (FIPS 10-4 country code) – (i) High Availability
- HAARP – (a) High Frequency Active Auroral Research Program
- HAART – (a) Highly Active Anti-Retroviral Therapy
- HAI – (i) Human Awareness Institute
- HAL – (i) Hardware Abstraction Layer
- HALO – (a) High Altitude Low Opening (parachute jump)
- HALT – (a) Hungry Angry Lonely Tired
- HAM – (s) Amateur radio operator
- HANS – (a) Head And Neck Support (device used in many race cars)
- HARM – (a) High-speed Anti-Radiation Missile
- hat – (s) Haitian Creole language (ISO 639-2 code)
- HAT – (i/a) Highest Astronomical Tide (nautical charts) – (a) Hungarian Automated Telescope
- hau – (s) Hausa language (ISO 639-2 code)
- HAW – (i) Heavy Antitank Weapon
- HAWK – (a) Homing All the Way Killer (air defence system)
- HAZ – (i) Heat-Affected Zone
- HAZMAT – (p) Hazardous Materials
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