Themvar template makes the argument italic and formats as mathematics. It is used to refer to individual variables in normal running text. It should not be used within a{{math}} template.
Note that digits in a variable name are conventionally not italic so{{math}} should be used instead in for example {{math|''x''<sub>1</sub>}} to producex1. Functions and variables made up of multiple letters are conventionally set in upright letters so{{math}} should be used in that case too; for example {{math|cos}} to producecos.
