Contrast

Balancing contrasting points

on the other hand; while; whereas

Arranged marriages are common in many Middle Eastern countries. In the West, on the other hand, they are unusual.

I like spending my holidays in the mountains, while/whereas my wife prefers the seaside.

While/whereas can be put before the first of 2 contrasting points,e.g.

While/whereas the English alphabet has 26 letters, English phonemic transcription has over 40 basic symbols.