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.
(..) I know nothing! I know nothing! I am a freak because of you! You made us freaks! And mom knew that! She understood! Unless it comes out of a fucking book, I don't know anything about anything! Dad. You should put some clothes on, buddy. (..)2016 Captain Fantastic
(..) Your words, but just words. - Not spoken in this house. - It's inappropriate in front... To say that in front of the kids. Absolutely. Understood. It won't happen again. Okay. Dad, how did aunt Leslie die? Well, aunt Leslie was sick, and she had complications (..)2016 Captain Fantastic