A punctilious person pays attention to details. Are you always precisely on time? Is your room perfectly neat? Do you never forget a birthday or a library book's due date? Then you are one of the punctilious people.
The adjective punctilious, pronounced "punk-TIL-ee-us," is related to the Italian word puntiglio, meaning "fine point." For someone who is punctilious no point is too fine, no detail too small, to be overlooked. The word is often used to describe people, but it can be used more broadly to apply to observations, behavior, or anything else that is characterized by close attention to detail.