Definition: A period of 100 consecutive years; often specifically a numbered period with conventional start and end dates, e.g., the twentieth century, which stretches from (strictly) 1901 through 2000, or (informally) 1900 through 1999. The first century AD was from 1 to 100.

Alright class, settle down, let’s take a look today – At a word that's tricky, in quite a way! We’re talking about “centuries,” you see, A measurement of time, for you and me. The dictionary says, it’s plain to find, “A hundred years, perfectly aligned!” Think of it like this, a lovely pace, Like a hundred summers, in a happy race. "Centuries" are groups, with dates we assign, Like the “twenty-first,” for this modern time! From 2001 onward, that’s where it starts, A numbered era, playing vital parts. But sometimes informally, you'll hear it said, “The twentieth century," from nineteen ninety instead – Nineteen hundred to nineteen ninety-nine, you see, That’s a common way for folks to agree! And the first one started, long, long ago, With "the first century AD," a historical flow. From one to one hundred, it truly did gleam, A foundational period, like a waking dream! Does that make sense? Any questions you might pose? Let's discuss!