In Spanish, the preposition a is used before a direct object that refers to a definite person. This is called “La a personal” (the personal a):
Los muchachos miran a las chicas. — The boys watch the girls.
Note that the personal a is not used when the object is not a person:
Los muchachos miran las olas. — The boys watch the waves.
The exception to this is the verb tener (to have). Even when the direct object is a person, tener does not use the personal a:
Tengo cuatro hermanos. — I have four brothers.
The use of the personal a is not a requirement for being understood in Spanish. If you forget to use it, don’t worry too much. Just listen carefully to Spanish speakers and you’ll eventually learn when to use it.
There are two important contractions is Spanish. When you sound them out it will become immediately clear why they are contracted.
The first contraction is de + el to form del (of the), as in:
La esposa del profesor. — The wife of the professor.
The second Spanish contraction is a + el to form al (to the):
María va al baile con Enrique. — Maria is going to the dance with Enrique.
The other combinations for ‘to the’ and ‘of the’ which are not contracted are:
of the -
to the -