A quart is a unit of measurement for volume.
It is equal to two pints.
There are several different units known as a pint, and so there are accordingly several different quarts.
Guide for the Use of the
International System of Units (SI) (http://physics.nist.gov/Document/sp811.pdf)
US government publication; includes US-(liquid)-to-litre & imperial-to-litre conversion
In imperial (UK & Canadian)
measure a quart is a measure of capacity, liquid or dry
Reference