However, some systems contain important variables that are equivalent to the chemical potential.

The three parts of a rule can contain variables for labels, trees, and forests.

The vector can also contain variables depending on a continuous index like a temperature field.

Sentences can also contain variables, strings starting with "?"

Packages can also contain global variables which can be used throughout the package.

Following this design, they conceptualized dimensions containing particular variables to analyze similarities and differences between the 18 countries under study.

They are also not sentences because they contain free variables:

Unlike quantum mechanics, the more complete theory contains variables corresponding to all the "elements of reality".

Seduction, it seemed, contained fewer variables and relied less on fate than did true love.

The data area contains global and static variables used by the program that are explicitly initialized with a value.