General:
* Pentagon: A five-sided polygon.
* Pentameter: A line of poetry with five metrical feet.
* Pentad: A group of five.
* Pentadactyl: Having five fingers or toes (e.g., humans, most mammals).
* Pentathlon: An athletic competition with five events.
* Pentacle: A five-pointed star used in witchcraft and other contexts.
Chemistry:
* Pentane: A hydrocarbon with five carbon atoms.
* Pentahydrate: A compound with five water molecules.
* Pentabromide: A chemical compound containing five bromine atoms.
Other:
* Pentatonic: Relating to a five-note musical scale.
* Pentacostal: Relating to the Pentecostal denomination of Christianity.
These are just a few examples. There are many other words that use the root "penta."