當行星在度數上形成某種配置，或某個相位即將在三度以內形成時，便稱之為「結合」（union）與「接近」（closing in）。
此外，當一顆運行速度較快的行星逐漸接近一顆運行速度較慢的行星，且兩者之間的距離不超過三度時，也稱為「接近」（closing in）。
某些作者認為，對於月亮而言，這些配置應以十三度的範圍作為判斷標準，因為月亮在一晝夜之間會運行十三度。
They call it a union and a closing in whenever there is a configuration by degree, or there is an aspect that is about to come together within three degrees. It is also termed closing in whenever a faster moving planet is approaching a slower moving planet, but the planets are no greater than three degrees apart from one another. Certain authors suggest that, in regards to the moon, these configurations should be considered within a span of thirteen degrees, because the moon travels 13 degrees in the course of one day and one night.