eyesight
n.the ability to see. You use this word to talk about how well or how poorly your eyes work.
n.the faculty or power of seeing; visual acuity. Refers to the physiological ability to perceive light and form.
“She wears glasses because her eyesight is poor.”
“Regular check-ups are essential to ensure your eyesight remains sharp as you get older.”
“The pilot's exceptional eyesight allowed him to spot the landing strip through the dense fog long before the instruments confirmed their position.”
Typically used with qualitative adjectives such as 'good', 'poor', 'failing', or 'diminishing'.
Eyesight is uncountable and does not take the indefinite article 'a'.
From Middle English eiȝesiht, ieȝesihte, ehsihthe, eihsihthe, eȝhesihthe, equivalent to eye + sight.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.