https://doi.org/10.1351/goldbook.P04819
Normal force acting on a surface divided by the area of that surface. For a mixture of gases the contribution by each @[email protected] is called the @[email protected] \(p_{i}=x_{i}\ p\), where \(x_{i}\) is the @[email protected] of the \(i\)th @[email protected] and \(p\) is the total pressure.