# Helmholtz free energy

## English

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### Etymology

For Hermann von Helmholtz German physicist

### Noun

1. () A measure of the useful work obtainable from a constant temperature, constant volume thermodynamic system; more precisely, the difference between internal energy (of a system) and the product of its absolute temperature and entropy.
$A = U - T S$ where A is Helmholtz free energy, U is internal energy, T is temperature, and S is entropy.