Plain English Meaning

A standard amount of liquid — a quarter of a gallon, or about a liter. Pilots most often see it on oil bottles and in the airplane's oil capacity figures.

Full Definition

A unit of liquid volume equal to one-quarter of a gallon. In U.S. measure, one quart equals 32 fluid ounces, or approximately 0.946 liters. In aviation, it is most commonly used to measure engine oil quantity.

Context Anchor

You will usually see this during preflight when checking the engine oil level or deciding how much oil to add.

Derivation

From the Latin 'quartus,' meaning 'fourth.' A quart is literally one-fourth of a gallon — the name carries the math.

Why Pilots Care

Engine oil must be maintained at the correct level in quarts to ensure proper lubrication and prevent engine damage.

Intuition Check

A U.S. quart and a U.K. (Imperial) quart are not the same. A U.S. quart is about 0.946 liters; an Imperial quart is about 1.136 liters. documents and U.S.-built use the U.S. quart.