Description: 从地球上的观测者的角度来看，当两个天体在天空中看起来非常接近时，它们被称为处于合相（合）。合相不一定是肉眼可见的——例如，每当新月时，月亮和太阳近似在一条直线上，但在此时，我们看不到月亮，除非发生日食。在这种情况下，或者两个天体非常接近（合）以至于一个天体看起来遮住另一个天体时，天文学家就会将其描述为凌日或食。

Related Terms:

• 日蚀
• 月相
• 冲
• 凌

Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

If you notice a factual or translation error in this glossary term or definition then please get in touch.