What does acclimatisation mean?
Acclimatisation is the noun describing the process by which a person, animal, or organism becomes accustomed to a new climate, environment, or set of conditions. Most commonly associated with high-altitude mountaineering — where the body must gradually adjust to reduced oxygen levels — the term also applies to shifts in temperature, humidity, and time zones, as well as metaphorically to settling into unfamiliar workplaces, cultures, or routines. The word is the standard British English form, while American English typically uses 'acclimation'. It appears frequently in scientific, medical, sporting, and travel writing, carrying a neutral, factual tone. Related forms include the verb 'acclimatise' and the adjective 'acclimatised'. Understanding acclimatisation matters because it underpins practical decisions in fields ranging from athletics and aviation to animal husbandry and human migration, where the pace of adjustment can determine health, safety, and performance outcomes.
nounThe process of becoming accustomed to a new climate, environment, or set of conditions. It can also refer more broadly to gradual physiological or psychological adjustment to unfamiliar circumstances.
- Physiological adjustment to a new climate or environmental conditions, especially altitude or temperature.
- Broader adaptation or habituation to any new situation, environment, or set of circumstances.
"After a week of acclimatisation to the high altitude, the climbers were ready for the summit push."
"The expedition included several days of acclimatisation at base camp before the ascent."
"New employees typically need a period of acclimatisation before they feel fully at ease in the office."
Rarely pluralised; the uncountable singular form is almost always used, even when referring to multiple instances of adjustment.
"The athletes underwent separate acclimatisations for heat and altitude training."
Mountaineers can spend weeks on acclimatisation before attempting a summit — skip it, and altitude sickness can strike within hours.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of acclimatisation
Acclimatisation derives from the verb 'acclimatise', which combines the prefix 'ac-' (from Latin 'ad-', meaning 'toward') with 'climate', itself from Greek 'klima', meaning 'slope' or 'region', via Latin 'clima'. The word entered English usage in the nineteenth century, coinciding with growing European interest in tropical exploration and colonisation, when questions of whether humans could adapt to foreign climates were widely debated. Its American counterpart, 'acclimation', follows the same root but drops reference to climate directly.
Related word forms
How acclimatisation is actually used
Primarily used in British English; American English strongly prefers 'acclimation'. The word carries a neutral, often scientific or medical register, appearing frequently in contexts of mountaineering, sports science, biology, and relocation.
Easily confused with acclimatisation
Acclimation is the standard American English spelling and term, while acclimatisation is the British English form; both refer to the same process of adjusting to a new climate or conditions.