Numbers: Circa

March 6, 2008: Issue 229

Circa is a preposition meaning around. It doesn’t need further hedging, or any other prepositions.
redundant: They built the house in circa 1860.
redundant: They built the house roughly circa 1860.
correct: They built the house circa 1860.

As with about and similar qualifiers, use circa with a general date or figure. If you have the exact date, you don’t need circa.
     unnecessary: She was born circa May 12, 1801.
correct: She was born May 12, 1801.
correct: She was born circa 1800.

Because circa implies a range, you need only one date or figure.
unnecessary: The first such lamps were made circa 1800-1810.
correct: The first such lamps were made circa 1800.
correct: The first such lamps were made between 1800 and 1810.

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