光線聚成的一點
畫面本身：真的有光，真的交會在一點上。這是這個詞最原本、最具體的一層。
noun · C1
In science: the point where rays of light meet after they have passed through a lens or bounced off a curved mirror.
焦點（光學）
核心畫面
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，…更多收起
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。Two branches
目光與活動聚過來的中心
同一個「聚成一點」的畫面，交會的東西從光換成了目光、話題和人潮。
noun · B2
The person or thing that everyone's attention goes to; the centre that an activity, a room, a picture, or a discussion is built around.
焦點；重心