Normally, it is supposed to be used within brackets, [sic] to show that a quoted passage, especially one containing some error or something questionable, is precisely reproduced, or written, just as the person who is being quoted wrote it.
It is to be read exactly as it is shown because that’s the way it was written in the original quotation.
Inserted to confirm a quotation even when the original is incorrect. It is inserted in brackets [sic] to indicate that the copy follows the original exactly as it was written or to show that a quoted passage; especially, one containing some error or something questionable, is precisely reproduced, or written, just as the person who is being quoted wrote it.
It is inserted in a quotation when the writer who is quoting wishes to disclaim responsibility for some error in grammar, spelling, or fact; and it is shown because that’s the way it was written in the original quotation; such as, "There's [sic] several reasons why we shouldn't do this." "This is the song that they sung [sic]."
"A subsequent memo . . . concluded that the 'doctors will submit one invoice which will include the special payments formally [sic] being made to their spouses along with there [sic] normal consulting services fee.' "
Another [sic] was seen in the St. Louis Post-Dispatch on September 6, 1998, in the sports section: "Even the best rookie backs loose [sic] their grip in the NFL."
Never use a period after sic, in or out of the brackets. It is not an abbreviation.
2. Corrupt in a spiritual or moral sense: "His sense of humor was vulgar and no one laughed at his sick jokes."
3. Filled with anxiety: "She was sick with worry before her daughter finally came home late from school."
4. Emotionally unsound or disordered: "Her mind was sick and she had to be psychologically treated for several months."
At first she thought that she was sic [sic] with fear that her angry neighbor would sic his dog on her; however, she later determined that she was just sick with the flu.