The term "circa" is used to indicate that a specific date or period is approximate or around that time. It is often abbreviated as "c." or "ca." and is commonly used in historical contexts to denote the estimated time of an event, especially when exact dates are unknown or uncertain. For example, when writing about events in history, you might say "circa 500 BC" to indicate an approximate date around that time.
The word "circa" comes from Latin, where it means "around" or "about." It has been adopted into English mainly in historical writing and documentation.