dioptre
C2CEFR level
88/100Rarity: very rare
TechnicalRegister
The unit used to express the focusing power of a lens or the degree of a refractive error.
Your prescription has increased by half a dioptre in the left eye.
Rarity runs from 0 (a word everyone knows) to 100 (almost never seen outside specialist or literary writing). Level is the word's real difficulty on the CEFR scale, from A1 to C2.
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