ha
Abbreviation with 5 meanings
| Stands for | Hectare |
|---|---|
| Meanings | 5 |
| Categories | Units & Measurements, Medical, Transportation & Travel, Technology & Computing |
| Also written | HA |
ha has five meanings. The most common are Hectare (metric and SI unit) and Headache (neurology); it can also stand for Hawaiian Airlines, Hyaluronic acid (filler) and High availability.
Meanings of ha at a glance
| # | ha stands for | Context |
|---|---|---|
| 1 | Hectare | Units & Measurements › Metric and SI Unit |
| 2 | Headache | Medical › Neurology |
| 3 | Hawaiian Airlines | Transportation & Travel › Airline Code |
| 4 | Hyaluronic acid (filler) | Medical › Dermatology |
| 5 | High availability | Technology & Computing › Cloud Computing |
1. Hectare
Units & Measurements · Metric and SI Unit Abbreviations
A metric unit of land area equal to 10,000 square meters, a square 100 m on a side, or about 2.471 acres. Farmland, forests, parks and property are measured in hectares in most countries.
Example: The vineyard covers 12 ha of south-facing slopes above the river.
Formed from hecto- plus are (100 m²), the hectare is not an SI unit but is accepted for use with SI. A standard soccer pitch covers about 0.7 ha. Crop yields are reported in tonnes per hectare (t/ha); US corn averages roughly 11 t/ha, equivalent to about 175 bushels per acre.
2. Headache (HA)
Medical · Neurology Abbreviations
Charting abbreviation for headache, one of the most common reasons for neurology and emergency visits. Notes often qualify it by type (migraine, tension-type, cluster) and flag "red flags" such as sudden thunderclap onset, fever, neurological deficits or onset after age 50.
Example: C/o HA x 3 days, bifrontal, pressure-like, no fever or neck stiffness; neuro exam nonfocal.
Primary headaches, such as migraine and tension-type, are not caused by another condition, whereas secondary headaches result from problems such as bleeding, infection or raised pressure. The SNOOP mnemonic lists warning features that call for imaging. HA has unrelated meanings, including hyaluronic acid, hemolytic anemia and hepatitis A.
3. Hawaiian Airlines (HA)
Transportation & Travel · Airline Code Abbreviations
Hawaii's largest airline, based in Honolulu and serving interisland routes, the US mainland and Asia-Pacific destinations. Alaska Air Group completed its acquisition of the airline in 2024.
Example: Interisland hop on HA 147 from Honolulu to Maui takes just 35 minutes.
ICAO code HAL; callsign "Hawaiian." Founded in 1929 as Inter-Island Airways, it is often cited as having never had a fatal accident or hull loss in its history. Its tails show Pualani, a woman wearing a hibiscus flower. The Hawaiian brand continues within Alaska Air Group.
4. Hyaluronic acid (filler) (HA)
Medical · Dermatology Abbreviations
Natural sugar molecule in skin that holds water; in cosmetic dermatology, cross-linked HA gels are injected as dermal fillers to restore volume in lips, cheeks and folds. HA is also a common moisturizing ingredient in skincare.
Example: HA filler 1 mL to nasolabial folds; hyaluronidase available in clinic.
A key safety advantage of HA fillers is that they can be dissolved with the enzyme hyaluronidase. Rare but serious risks include injection into a blood vessel causing skin death or blindness. Effects usually last six to eighteen months. In general medicine HA usually means headache.
5. High availability (HA)
Technology & Computing · Cloud Computing Abbreviations
The design of systems to keep running with minimal downtime by eliminating single points of failure, using redundant servers, automatic failover, load balancing and replication across zones.
Example: The HA pair of firewalls fails over in under a second if the primary loses power.
Availability is often stated in "nines": 99.99 percent, or four nines, allows about 52 minutes of downtime a year. High availability handles routine failures within a site or region, while disaster recovery deals with larger catastrophes. Each additional nine usually multiplies cost and complexity.
Related abbreviations
More metric and SI unit abbreviations
- gsm – Grams per square meter
- Gt – Gigatonne
- Gy – Gray
- h – Hecto- (hundred)
- hL – Hectoliter
- k – Kilo- (thousand)
- kat – Katal
- kg – Kilogram
See all 64 metric and SI unit abbreviations →
More neurology abbreviations
- FAST – Face, Arm, Speech, Time
- FTD – Frontotemporal dementia
- GBS – Guillain-Barré syndrome
- GTC – Generalized tonic-clonic seizure
- HD – Huntington's disease
- HIE – Hypoxic-ischemic encephalopathy
- HINTS – Head Impulse, Nystagmus, Test of Skew
- ICH – Intracerebral hemorrhage
See all 131 neurology abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.