This is the 848th most frequent Spanish word.
trabaja
"(He/She) works" or "Work" (command).
In this sentence, "trabaja" is a verb in the third person singular, present tense, used to describe a habitual action performed by María.
María trabaja en una oficina todos los días.
María works in an office every day.
Here, "trabaja" is used metaphorically to indicate an object functioning or operating, applied to a mechanical device.
Este reloj trabaja a base de energía solar.
This watch works on solar power.
In this context, "trabaja" is used in the third person singular, present tense, suggesting a conditional outcome dependent on a person's actions.