The document discusses how English speakers express uncertainty in their language. It provides examples of Catherine and Elena speculating about whose eyes are in a picture on the BBC Learning English website, where they aren't certain and use language like "might", "could", and question tags. The document then explains that question tags, modal verbs like "might", and words like "maybe" and "perhaps" are common ways to convey uncertainty in English. Intonation is also important, as the same words can indicate different levels of certainty depending on how they are said.