Circa usually abbreviated c. or ca. (also circ. or cca.), means "approximately" in the English language

English language

English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...

, usually referring to a date. Circa is widely used in genealogy

Genealogy

Genealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...

and historical writing when the dates of events are not precisely known.

When used in date ranges, the term "circa" is applied before each approximate date, while dates without "circa" immediately preceding them are generally assumed to be known with certainty.

Examples:

• 1732–1799, both the years shown and the date range are precisely known–1799, only the second year shown is certain, the first year is approximately known
• 1732 – , in this case the first year is certain, and the second year is approximate – , both the years shown and the date range are approximately known