How to Say "to decompose" in Spanish
The Spanish word for “to decompose” is “pudrir” — B1 level.

Examples
Las manzanas se empezaron a pudrir en la cesta.
The apples started to rot in the basket.
La lluvia constante pudrió la madera de la cerca.
The constant rain rotted the wood of the fence.
Si dejas la basura ahí mucho tiempo, se va a pudrir.
If you leave the trash there for a long time, it's going to rot.
The 'O' to 'U' History
This verb used to be spelled 'podrir', but modern Spanish has standardized the infinitive to 'pudrir'. However, the adjective 'podrido' (rotten) still uses the 'o'!
Using the Reflexive Form
When something rots on its own, we usually add 'se' to the end: 'La comida SE pudre' (The food is rotting).
The Past Participle Trap
Mistake: “La fruta está 'pudrida'.”
Correction: La fruta está 'podrida'. Even though the verb is 'pudrir', the word for 'rotten' uses an 'o'.
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