noun
hour
OW-er/ˈaʊər/
A measured period of sixty minutes.
The clock's minute hand completes one full turn in an hour.

Etymology
Greek hōra could name a season or a portion of a day. The modern sixty-minute hour reflects the fixed division of a full day into 24 equal parts, unlike older daylight hours that varied with the seasons.
In context
you probably glance at a clock without thinking twice, but why does an hour have 60 minutes and a minute have 60 seconds?