Noon is the moment when the sun reaches its highest point in the sky, marking the middle of the day, which we usually call 12:00 p.m. It's when morning officially ends and afternoon begins.

Before clocks were invented, people determined noon by observing when shadows were shortest, since the sun was close to directly overhead.

Noon serves as an important reference point beyond simply telling time. For thousands of years, ships at sea used noon to navigate: sailors would measure the sun's height at its peak to calculate their latitude (how far north or south they were). Farmers planned their workdays around noon, often taking breaks during the hottest part of the day. Many towns had noon whistles or bells to help everyone synchronize their activities.

Today we use noon as a reference point: meetings are scheduled for “before noon” or “after noon,” which is where we get the abbreviations a.m. (ante meridiem, “before midday”) and p.m. (post meridiem, “after midday”). When someone says high noon, they're emphasizing the exact middle of the day. The word can also describe the peak or highest point of anything, like the noon of someone's career.