dioptre
/dʌɪˈɒptə
/(US diopter)
noun
A unit of refractive power, which is equal to the reciprocal of the focal length (in metres) of a given lens: vision corrected to within one dioptre of perfect sight...
- The focusing power of a lens is measured in dioptres.
- Refractive error is measured in dioptres, and myopia is designated with a minus sign.
- The difference between the focusing powers of these two axes, measured in dioptres, is the astigmatism.
Origin
Late 16th century (originally as diopter, denoting an alidade): from French, from Latin dioptra, from Greek, from di- 'through' + optos 'visible'. The term was used in the early 17th century to denote an ancient form of theodolite; the current sense dates from the late 19th century.
Rhymes
- carbon credit
- carbon cycle
- Carbondale
- carbon-date
- carbon dating
- carbon debt
- carbon dioxide
- carbon dioxide snow
- carbon disulfide
- carbon disulphide
- carbon emission
- carbon fibre
- carbon fixation
- carbon footprint
- carbon-free
- carbonic
- carbonic acid
- carbonic acid gas
- carbonic acid snow
- carbonic anhydrase
- carbonic oxide
- carbonic snow
- Carboniferous
- Carboniferous limestone
- carbonification