syzygy
noun [ C or U ] physics specialized uk/ˈsɪz.ə.dʒi/ us/ˈsɪz.ə.dʒi/
朔望
an arrangement in which two or more planets, stars, etc. are in a straight line
When the Moon is in syzygy with the Sun and Earth, there can be noticeable gravitational effects. 当月球与太阳和地球处于朔望位置时，会有明显的引力效应。