本初子午線

1. • the first meridian
2. • the prime meridian

Character by character

• 本(běn)root
• 初(chū)at first
• 子(zǐ)son
• 午(wǔ)7th earthly branch: 11 a.m.-1 p.m., noon, 5th solar month (6th June-6th July), year of the Horse
• 線(xiàn)thread