“擅离”常见的英文表达可以是 “leave one's post without permission” 或 “unauthorized departure”，具体使用哪个取决于语境：
“leave one's post without permission” 强调未经许可离开岗位，比较正式和具体，适用于描述工作、军事或其他有明确职责和岗位要求的场景。例如：The soldier was punished for leaving his post without permission.（这个士兵因擅离岗位而受到惩罚。）
“unauthorized departure” 侧重于未经授权的离开，适用范围更广，可用于各种非正式或正式场合。例如：His unauthorized departure from the meeting caused some confusion.（他未经许可离开会议，造成了一些混乱。）