A liter is a specific measurement of volume. Volume is
the amount of three dimensional space enclosed by a
closed boundary. Volumes typically are used to refer to
liquids but they are sometimes used in reference to
gasses and solids. A liter is equal to 1.056688 quarts.
To understand this better, picture a gallon of milk. It
takes 4 quarts of milk to make up one gallon of milk.
Since one liter is a little bit more than one quart, 4 liters
of milk is a little bit more than one gallon of milk. It takes
one thousand milliliters to equal one liter as you can see
in the picture. One milliliter is equal to one cubic
centimeter (often referred to as “cc”) and one cubic
decimeter (abbreviated as dm3). These measurements
are based on those used in the United States.

"Where Medical Information is Easy to Understand"™
FEATURED BOOK: Oxford Dictionary of Weights, Measures, and Units

Liter is often abbreviated as "L" or "l." However, it is recommend that the upper case “L”
is used since the lowercase “l” can easily be misread as the number “1.”

If the lowercase “l” is used it is sometimes written is cursive so it is not confused with
the letter “I” or the number “1.” Liter is sometimes spelled as litre.

Liter comes from the Greek word "litra" meaning "pound."