a period of 100 years
"The bridge was completed just before the turn of the century, making it over a hundred years old now."
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.
"Historians debate whether the year 1900 marked the beginning of the twentieth century or if that honor belongs strictly to 1901."
In plain English: A century is a period of time that lasts for one hundred years.
"They have lived in this house for over a century."
Usage: A century is a period of exactly one hundred consecutive years, such as the twentieth century strictly spanning from 1901 to 2000. Use this term to denote either any arbitrary 100-year block or a specific numbered era in history, keeping in mind that historical centuries begin with year one rather than zero.
The word entered English via Middle English and Old French from the Latin centuria, which originally referred to a count of one hundred items or a division of the Roman army. While it once described various groupings of a hundred, its most common modern use is as a period of one hundred years.