"Metrum" means "measure" in Latin, and it is the root of many English words related to measurement, rhythm, and poetry, such as:
* Meter: a unit of measurement (e.g., a meter stick)
* Metric: a system of measurement
* Rhythm: a pattern of sounds or movements
* Metronome: a device used to keep time in music
* Poetry: written work with a rhythmic structure
The "metron" prefix often signifies "measure" or "rhythm" in compound words.