ancient
Very, very old, from a time long ago.
Ancient means very, very old, from a time long ago. When historians talk about ancient civilizations, they mean societies that existed thousands of years before our time: ancient Egypt with its pyramids, ancient Greece with its philosophers and Olympics, or ancient Rome with its mighty empire. These places thrived so long ago that we learn about them through ruins, artifacts, and old writings rather than photographs or recordings.
Something ancient doesn't just predate your grandparents or even your great-great-grandparents: it reaches back through countless generations to eras when people lived completely different lives, without electricity, cars, or modern medicine.
You might call a 200-year-old oak tree ancient, or describe your school's outdated computer as ancient (even though it's probably only ten years old). When used this way, the word exaggerates for effect. But in history class, ancient usually refers to periods ending around 1,500 years ago, when the Western Roman Empire fell.
The opposite of ancient is modern or contemporary. An antiquity is an object from ancient times, while someone who studies ancient civilizations is called a classicist or an archaeologist.