There are two articles used with nouns: en and et. The article is placed before the noun.
| en hund | a dog |
| et hus | a house |
Words with en are called n-words.
Words with et are called t-words.
There are, unfortunately, no rules that tell us when to use en, and when to use et.
Comparison:
In English we have the indefinite articles a and an. A is used in front of a vowel, an in front of a consonant.
a man
an apple