To purloin something is to take it without asking. The meaning sits next to steal, but the feeling is lighter. People often use it with a small smile: someone has purloined the last biscuit, or a colleague has purloined your pen. You would not normally use it for a serious crime — a bank robbery is not “purloining.” It sounds a bit old-fashioned and a bit playful, the kind of word a teacher or a caption might choose instead of steal, so the taking feels small and almost cheeky. In dry or legal writing it can still appear, but then it can sound stiff. In everyday talk, steal is what people actually say (and in British English, nick).

順手牽羊、偷走（多帶戲謔，不像嚴重犯行）