What is the difference between 变 (biàn) and 易 (yì)? I would say that both 变 (biàn) and  易 (yì) have the same (or very similar) meaning, dealing with &quot;something that changes&quot;, like in &quot;易经&quot; (the Book of changes)  or &quot;变温层&quot; (troposphere).
Is this assumption correct?
What are differences and similarities? In which context one should be used in place of the other?
变 is mainly used as a verb for &quot;change; alter; turn (e.g. turn into a dog)&quot;

易 is mainly used as a verb component in a compound word. Mostly indicates 'transfer' (from one to another). 易 is not used as a verb on its own in day to day speech in modern Chinese


Look at the compound words contain these two characters
变化 - change
转变 - change; transform
易手 - change hand -- transfer ownership
交易 - exchange -- mutually transfer goods or money