The term apse is specific to church buildings and is a key element in their architecture.

Church Architecture

While commonly rounded, apses can be polygonal or flat-ended in some churches.

Not Always Rounded

An apse can be a decorative and functional part of secular buildings, not just churches.

In modern contexts, apse can refer to new additions or features in contemporary architecture.

In astronomy, 'apse' relates to specific points in a celestial body's orbit, not physical structures.

'Apse' is used to describe the extreme points in an object's elliptical orbit; closest and furthest.