Hold a magnifying glass over a sheet of paper on a sunny day. Sunlight arrives spread out and flat, goes through the glass, and all of it crosses at one small bright spot. Nothing has been added — the same light is simply gathered into one place, and that place is where things happen. That spot is the focal point. Swap the light for people's eyes, or for what a whole discussion keeps coming back to, and you have the everyday use: the one place everything converges.
晴天時把放大鏡舉在一張紙上方。陽光原本是散開、平平地灑下來的，穿過鏡片之後，全部交會在一個很小的亮點上。光沒有變多，只是被收攏到同一個地方，而事情就在那裡發生。那個亮點就是 focal point。把光換成大家的目光，或換成一場討論一直繞回去的那件事，就得到日常的用法：所有東西聚過來的那一點。
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