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.
(..) these very rare, brief instances, in which you suddenly remember... you can swim. But, then again, mostly not. Mostly you're drowning. She understood that too. And she recognized that I understood it. And Dad. All three of us were drowning, and we didn't know how to save each other, (..)2018 TvShow: BoJack Horseman Title: Free Churro Season: 5 Episode 6
(..) And as a child who was completely terrified of both my parents, I was always aware that this moment of grace, it meant something. We understood each other, in a way. Me and my mom and my dad, as screwed up as we all were, we did understand each other. My mother, she knew (..)2018 TvShow: BoJack Horseman Title: Free Churro Season: 5 Episode 6