Because the first letter of a university is U. In English, A can be used in front of a university because the first letter of a university is U, which is a consonant, and A is used in front of words that start with consonants, so A can be used in front of a university. University can be used as a noun. The basic meaning of a university is a university, which usually refers to a comprehensive university composed of several colleges. It can be used as both countable and uncountable nouns.