Zd
n. 天顶距（zenith distance）；零色散（Zero Dispersion）
🗣️ 情景例句
I didn't realize how late is was.
我不知道已经这么晚了。
They could imagine who was at the door.
他们无法想象门那边有谁在。
I'd say about half of the shipment is unusable.
我看大概有一半的货不能用了。