In Western society, "underground" or "alternative" are words which are often used alternately to describe a thing as it changes with the times and becomes difficult to define.
在西方社會裡，所謂「地下」（Underground）、「另類」（Alternative），經常是交替使用，用以表示同一個事物在不同時代裡的消長變化，難以確切定義。