"Del" and "Al"

In Spanish, when the preposition "de" or the preposition "a" is followed by the definite masculine article, "el," the two combine to become "del" and "al": 

Incorrect: Estoy en camino a el cine. 
Correct: Estoy en camino al cine. 

Incorrect: Eso es el carro de el policía. 
Correct: Eso es el carro del policía. 

Remember, you only need to do this with the  "de" + "el" and "a" + "el" combinations; no other definite article forms contractions like this.

Check out this article for additional insight into these common contractions: 

http://www.spanishdict.com/topics/show/11