When people say “they're engaged,” the phrase “to be married” 'is understood'. [=“they're engaged” is understood to mean “they're engaged to be married”]
We still don't fully 'understand' the causes of the disease. = The causes of the disease are still not fully 'understood'.
He believed it 'was understood' [=believed that everyone had agreed] that he would be paid for the work.
(..) back your graded quizzes. I urge you to find the problems where you went wrong, and work them out. Good job, Jules. I could tell from your work that you even understood he one you missed! Suck a dick. I like "Jules". I just don't get why I'm not good at math, my Dad is really good at math. (..)2017 Lady Bird