Picture a chart that sorts something into levels, and first-degree is the box at the top of the chart. What the chart does not tell you is which end is the bad end. A burn chart starts counting at the mildest injury, so first-degree is the gentle one. An American murder chart starts counting at the worst crime, so first-degree is the heaviest one. The word marks the first step; the chart decides what that step holds.
可以想成一張把東西分級的表，first-degree 就是表上的第一格。表本身不會告訴你「第一格」是輕還是重。燒燙傷那張表從最輕開始排，所以 first-degree burn 最輕。美國殺人罪那張表從最重開始排，所以 first-degree murder 最重。同一個 first，輕重相反，關鍵永遠在你手上是哪一張表。degree 在這裡就是「級」，不是溫度，也不是學位。