acuity

Everyday

1. (formal) Sharpness of a sense, especially of eyesight or hearing: «visual acuity» means how clearly you can see small details. tree →
2. (formal) Sharpness of the mind: being quick to notice and understand things. tree →

In the lessons

In science and health lessons, eye tests measure visual acuity with a chart of letters getting smaller. Doctors say «20/20» (US) or «6/6» (UK) for normal acuity. In stories it describes a detective's sharp mind. Phrases: «visual acuity», «mental acuity».

Examples

• The eye test measured my visual acuity. tree →
• Eagles have amazing visual acuity and can spot a mouse from high up. tree →
• The detective's acuity helped her solve the case. tree →
• Older dogs can lose some hearing acuity. tree →
• The optician said my acuity is better with glasses. tree →
• Owls have great acuity in the dark. tree →

Note

Formal word; everyday words are «sharpness», «how well you see». Say «uh-KYOO-it-ee». Related: «acute» (sharp; also an acute angle, less than 90 degrees). Not «accuracy», though they are related in meaning.