Every synthesis has two endings. On paper, stoichiometry works out a maximum — the theoretical yield, a prediction computed before the flask is even dirty. In the flask, after filtering and drying, sits whatever you actually made — the actual yield, a mass that sat on a real balance. The paper number is a ceiling; the flask number is a fact. Real runs leak — product clings to filter paper, side reactions skim reagents — so the fact almost always undercuts the ceiling.

The percent yield referees between them: $\%\,\text{yield} = \dfrac{m_a}{m_t} \times 100$ — read aloud: percent yield equals m-a over m-t, times one hundred, where $m_a$ (m-a, the actual) is the flask's fact and $m_t$ (m-t, the theoretical) is the paper's promise. This lesson only asks you to tell the three apart — and the words and units are the tells: weighed means actual, computed means theoretical, and a % sign means the referee.