This is the 3283rd most frequent Spanish word.
caía
"Caía" means "was falling" or "used to fall."
'Caía' here is metaphorically used to indicate the action of the sun 'falling,' illustrating the imperfect tense to portray a gradual past event.
El sol caía lentamente detrás de las montañas.
The sun was slowly setting behind the mountains.
In this example, 'caía' conveys a lowering or decreasing action in a habitual past context, again in the imperfect tense.
El nivel de agua en el río caía debido a la sequía.
The water level in the river was dropping due to the drought.
In this sentence, 'caía' is used as the imperfect tense of the verb 'caer', describing an ongoing action in the past.