Mi hermana prefiere enjuagar la fiambrera a mano porque dice que así queda más limpia.

My sister prefers to rinse the lunch box by hand because she says that this way it gets cleaner.

Breakdown of Mi hermana prefiere enjuagar la fiambrera a mano porque dice que así queda más limpia.

• mi: my
• limpio: clean
• que: that
• más: more

Questions & Answers about Mi hermana prefiere enjuagar la fiambrera a mano porque dice que así queda más limpia.

Why is it prefiere and not prefera or prefería?

Prefiere is the 3rd person singular present tense of preferir: (él/ella) prefiere = he/she prefers.

This verb is a stem-changing verb in the present tense:

• yo prefiero
• tú prefieres
• él/ella prefiere
• nosotros preferimos
• vosotros preferís
• ellos/ellas prefieren

So Mi hermana prefiere... means My sister prefers...

• prefera is not a correct form here.
• prefería would mean used to prefer / would prefer, which changes the meaning.

Why is enjuagar in the infinitive after prefiere?

After preferir, Spanish commonly uses an infinitive when talking about preferring to do an action.

So:

• prefiere enjuagar = prefers to rinse
• literally: prefers rinsing / prefers to rinse

This is very common in Spanish:

• Prefiero comer en casa. = I prefer to eat at home.
• Prefieren esperar. = They prefer to wait.

You do not need de here.
So prefiere enjuagar is correct, not prefiere de enjuagar.

What exactly does enjuagar mean here?