clairance

Clairance is a term that appears primarily in French-language technical literature and occasionally as a loanword or misspelling in English. In English usage, the standard term for the related concepts is clearance. Clairance can therefore be encountered in bilingual texts or older writings, but it is not common in modern English technical vocabulary.

In engineering and manufacturing, clairance refers to the intentional gap between mating parts. This gap allows relative motion, lubrication, and accommodation of manufacturing tolerances and thermal expansion. The size of clairance directly affects fit, movement, and wear characteristics of mechanical assemblies. In architectural and civil contexts, clairance is used to describe available space or headroom, such as clearance heights under structures, doorway or passage widths, and other spatial requirements that ensure safe passage or operation of equipment.

In addition to technical senses, clairance can appear in French-influenced discussions of permissions or approvals, where clearance is the equivalent English concept. However, in English-language writing today, clearance is the preferred term for both space and permission meanings. When translating or adapting French technical documents, clairance may be retained as a loanword, but care should be taken to avoid conflating it with the standard English term clearance.

See also: clearance, headroom, tolerance, fit.