The Latin adverb sic (pronounced [siːk]; "thus", "just as"; in full: sic erat scriptum, "thus was it written") inserted after a quoted word or passage indicates that the quoted matter has been transcribed or translated exactly as found in the source text, complete with any erroneous, archaic, or otherwise nonstandard spelling, punctuation, or grammar. It also applies to any surprising assertion, faulty reasoning, or other matter that might be interpreted as an error of transcription.

The typical usage is to inform the reader that any errors or apparent errors in quoted material do not arise from errors in the course of the transcription, but are intentionally reproduced, exactly as they appear in the source text. It is generally placed inside square brackets to indicate that it is not part of the quoted matter.

Sic may also be inserted derisively or sarcastically, to call attention to the original writer's spelling mistakes or erroneous logic, or to show general disapproval or dislike of the material.