What does acclimatise mean?
To acclimatise is to become accustomed to a new climate or set of environmental conditions — or, when used transitively, to bring someone or something to that state of adjustment. The word is most at home in contexts of physical adaptation: mountaineers acclimatise to thin air, travellers to tropical heat, and horticulturists deliberately acclimatise seedlings before planting them outdoors. By extension it can describe adjusting to unfamiliar surroundings generally, though its core sense remains tied to climate and environment. The spelling with '-ise' is standard in British English, while American usage favours the shorter 'acclimate'. The word's structure is unusually transparent: it visibly contains 'climate', signalling its literal concern with weather and atmosphere. Neutral in tone and common in both scientific and everyday registers, it is a precise alternative to vaguer words like 'adjust', especially whenever temperature, altitude, or humidity are involved.
verbTo become, or cause someone or something to become, accustomed to a new climate or new conditions.
- (intransitive) To become accustomed to a new climate or environment.
- (transitive) To cause a person, animal, or plant to become accustomed to new climatic or environmental conditions.
"It took the climbers several days to acclimatise to the thin air at high altitude."
"Athletes arriving early for the marathon used the extra week to acclimatise to the humid conditions."
"The nursery gradually acclimatises seedlings to outdoor temperatures before sale."
The word literally contains 'climate' inside it — acclimatise is, quite transparently, the act of making yourself at home in a climate.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of acclimatise
Acclimatise derives from French 'acclimater', formed from the Latin root 'clima' (ultimately Greek 'klima', meaning inclination or zone), combined with the intensive prefix 'ac-'. The word entered English in the nineteenth century as interest in colonial exploration, botany, and human settlement in foreign climates grew — societies dedicated to 'acclimatisation' were founded in Britain and France during this period. Its cognates include the direct borrowing 'climate' and the American-favoured shortened form 'acclimate'.
Related word forms
How acclimatise is actually used
The spelling 'acclimatise' is standard in British English, with 'acclimatize' an accepted variant; American English typically prefers 'acclimate' or 'acclimatize'. The verb works both transitively and intransitively, though the intransitive use ('to acclimatise to something') is by far the more common. It carries no strong register — it appears equally in scientific writing about plants and animals and in everyday talk about travel and sport.
Easily confused with acclimatise
'Acclimate' is the shorter American-preferred variant of the same verb, while 'acclimatise' is the British spelling that explicitly retains the '-climate' element.