A jump cut is usually the result of a continuity error, and not a stylistic choice by the director. A jump cut occurs when a cut, designed to act merely as a camera angle change (less than 30-degrees), reveals a continuity discrepancy between the two shots. For instance, if a character has their hand over their mouth in a medium shot, and not in their close-up, this little detail, which probably was not noticed on set, is now painfully obvious to the viewers.