Normal force acting on a surface divided by the area of that surface. For a mixture
of gases the contribution by each
constituent is called the
partial
pressure
,
where

is the
amount fraction of the

th
constituent and

is the total pressure.
Source:
PAC, 1996, 68, 957
(Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations
1996))
on page 987