Breakdown of La niña tiene lágrimas en los ojos, debe de estar triste.
la niña
the girl
tener
to have
en
in / on / at
triste
sad
Questions & Answers about La niña tiene lágrimas en los ojos, debe de estar triste.
Why is it debe de estar instead of just debe estar?
Deber de followed by an infinitive like estar is specifically used to express a strong assumption or probability, translating to "must be" in the sense of "I suppose she is." If you drop the de, deber usually expresses an obligation, meaning what someone "has to" do. While native speakers sometimes drop the de for assumptions in casual speech, using debe de estar makes it perfectly clear that you are guessing she is sad, not ordering her to be sad!
Why does the sentence use en los ojos (in the eyes) instead of en sus ojos (in her eyes)?
In Spanish, it is standard to use the definite article (el, la, los, las) rather than possessive adjectives (mi, tu, su) when talking about body parts. Because the first half of the sentence is already focused on la niña, it is obvious whose eyes are watering, so los ojos is the most natural and grammatically correct way to say "her eyes."
Why do we use estar triste here instead of ser triste?