100 years is called a century. The computer, the television, and video games were all invented in the twentieth century. People are now wondering what the twenty-first century holds for us.
The noun century comes from the Latin word centuria, which was a group of 100, particularly a group of 100 Roman soldiers (one of 16 such groups in a Roman legion). The word today still can refer to 100 of something. In sports, a century is a score of 100 in a game of cricket. A race of 100 yards or 100 miles is also sometimes called a century. In slang, century can also mean a 100 dollar bill.