It looks like this, eta. You can write it all at once.

Eta (capital η, lowercase η) is the seventh Greek letter.

η is the symbol of mechanical efficiency, which refers to the percentage of output work (useful work) and input work (dynamic work) of machinery.

η has many functions in science:

Thermodynamically, the efficiency of Carnot cycle.

Physically, η is used as the refractive index of optical medium; Mechanical efficiency.

Statistically speaking, eta? Used as a partial regression coefficient.

Chemically, the label η n in front of the ligand indicates that its Harpto number is n.

In experimental particle physics, η is used as the pseudo-rapidity of moving particles.

The most common, η is mostly physical, and its main contents include pulley block, slope efficiency, lever transmission, common efficiency and increasing efficiency. We call the ratio of useful work to total work mechanical efficiency.