Circumstantial is a word that refers to specific details about something: in other words, about circumstances. Circumstantial evidence might implicate someone's guilt, but it certainly doesn't prove them guilty.
The word circumstances refers to the facts of your life: everyone has different circumstances. So the word circumstantial refers to the specific details of some situation. This word is most often heard in the term circumstantial evidence, which you may have heard on a TV crime or trial program. Circumstantial evidence might lead a detective to suspect someone's guilt, but eyewitness testimony may be needed to convince the jury.
