時間上的那扇門
這一支的門開在時間軸上：同一件事，換個時間就沒有效果。
adjective · C1
Done, said or arriving at exactly the right time, so that it works well or helps.
時機恰當的
核心畫面
Think of a door that stands open for a short while. Walk through while it is open and the thing you wanted goes smoothly; come a minute early or a minute late and the same words, the same act, get you nowhere. Opportune is the label for that open door — and sometimes the door is a point in time, sometimes it is a place or a thing that happens to be exactly where you need it.
opportune 可以想成一扇只開一下下的門。門開著的時候走過去，事情就順；早一步或晚一步，同樣的話、同樣的動作就…更多收起
opportune 可以想成一扇只開一下下的門。門開著的時候走過去，事情就順；早一步或晚一步，同樣的話、同樣的動作就沒有效果。這個字標的就是那個「門開著」的位置。多數時候那扇門是一個時間點，偶爾也可以是一個剛好在那裡、剛好合用的地方或東西。Two branches
地點上的那扇門
同樣是「剛好對上」，只是這次對上的不是時鐘，而是一個地方或一樣東西。
adjective · C2
Suited to what you need at that point — used about a place or a thing that happens to be just right for the purpose.
（地點、東西）正合用的