Ma'anar "tsayin sararin sama" yana nufin nisan kwana tare da husufi, wanda aka auna gabas daga ma'aunin da'irar vernal har zuwa inda husufin ya hadu da ma'aunin sararin samaniya, ga wani abu na sama kamar tauraro ko tauraro. Yawanci ana auna shi cikin digiri, mintuna, da daƙiƙa. Ana amfani da tsayin daka a sararin samaniya don tantance wurin da abubuwan sararin sama suke dangane da vernal equinox, wanda yana daya daga cikin abubuwan da ake amfani da su a cikin tsarin haɗin gwiwar sama.