Horology

Horology (via Latin horologium from Greek ὡρολόγιον, from ὥρα hṓra "hour; time" and -o- interfix and suffix -logy; literally "the study of time") is the art or science of measuring time. Clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clocks are all examples of instruments used to measure time. In current usage, horology refers mainly to the study of mechanical time-keeping devices, while chronometry more broadly includes electronic devices that have largely supplanted mechanical clocks for the best accuracy and precision in time-keeping.