measles
The Spanish word 'sarampión' translates to 'measles' in English. Measles is a highly contagious virus that exists in the nose and throat mucus of an infected person. It can spread to others through coughing and sneezing. The virus is so contagious that if one person has it, up to 90% of the people close to that person who are not immune will also become infected. The disease was once very common in the U.S. but became rare after vaccination started in the 1960s.
My brother had measles when he was young.
This sentence is using the past-tense verb 'tenía' (had) to indicate that the speaker's brother had measles when he was younger. 'Sarampión' is used here as the object, the thing that the brother had.
Measles is a highly contagious disease.
This sentence is describing measles (sarampión) as a highly contagious disease. 'Es' (is) is the verb here, and 'una enfermedad altamente contagiosa' (a highly contagious disease) is the predicate, or the part of the sentence that explains something about the subject.
The measles vaccine is very important.
In this sentence, 'sarampión' is used in a compound noun with 'vacuna' (vaccine) to describe a particular type of vaccine. The predicate, 'es muy importante' (is very important), is describing this compound noun.