adj \(ˈ)par-ˈak-sē-əl\

Definition of PARAXIAL

: relating to or being the space in the immediate neighborhood of the optical axis of a lens or mirror <paraxial rays>
par·ax·i·al·ly \-ē\ adverb

Seen & Heard

What made you want to look up paraxial? Please tell us where you read or heard it (including the quote, if possible).