Para siempre vs. por siempre
The Spanish phrases 'para siempre' and 'por siempre' both translate to 'forever' in English, implying an indefinite period or eternity. While they can often be used interchangeably, subtle differences may exist.
Para siempre
'Para siempre' is often used to denote a lasting condition or state, typically expressing a desire or proclaiming an intention for something to last forever.
Voy a amarte para siempre.
(I am going to love you forever.)
Esta ciudad será mi hogar para siempre.
(This city will be my home forever.)
Por siempre
'Por siempre' tends to feel a bit more poetic or formal. This phrase leans more towards the definition of 'throughout all future time', indicating an unending process or repeatable action.
Tu eres mi amor por siempre.
(You are my love forever.)
Viviremos en paz por siempre.
(We will live in peace forever.)
Summary
'Para siempre' and 'por siempre' both translate as 'forever', but there is slight difference in usage. 'Para Siempre' is used more towards a permanent state whereas 'Por Siempre' signifies an ongoing process. However, many native Spanish speakers often use them interchangeably.