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.
(..) After we finish cleaning up this mess, we will go our separate ways. Our paths will never cross. And we will tell this to no one. Understood? What, I can talk now? Fine. That goes double for me. Be good to me. Oh, shit. (..)2008 TvShow: Breaking Bad Title: Cat's in the Bag... Season: 1 Episode 2
(..) I don't know what's been going on with you lately. You understood what I've just said to you? Lung cancer. Inoperable. You wanna cook crystal meth? You and me? You know the business. (..)2008 TvShow: Breaking Bad Title: Cat's in the Bag... Season: 1 Episode 2