Simple vs. sencillo
The Spanish words simple and sencillo are often used interchangeably, as they both refer to something being not complicated. However, there can be subtle differences in their usage based on context.
Simple
A2Simple is a more general term for describing something as not complex or complicated. It is the equivalent of the English word simple.
La vida es simple, nosotros la complicamos.
(Life is simple, we complicate it.)
Este es un plan simple.
(This is a simple plan.)
Es una solución simple para el problema.
(It's a simple solution to the problem.)
Sencillo
A2Sencillo is typically used to mean that something is easy or uncomplicated. It can also imply something that is humble or unpretentious. Furthermore, in some regions, it may refer to small money or change.
El examen fue muy sencillo.
(The test was very easy.)
Vive de manera sencilla.
(He lives in an unpretentious way.)
¿Tienes cambio sencillo?
(Do you have small change?)
Summary
Simple and sencillo both mean simple but can convey slightly different nuances. Simple is a more general term implying that something exists as a single element or is uncomplicated. Conversely, sencillo suggests that something is easy, humble, or unpretentious and in certain situations could refer to small denomination money.