The nouns have one of three genders, either masculine, feminine or neuter. (hankyn, hokyn, inkjekyn)
As an example we can use four words with different genders:
As you can see there's two categories for the feminine gender, the first one is a lot more common. Both are treated the same except in certain declensions of the word itself.
Now, what do we write when we want to say something like 'a day' or 'the day'?
Like in English 'a day', the indefinite article is before the word...
but with 'the day' we have to change the end of the word itself.
Singular definite suffixes
Try it out for yourself! Match them with the words we have. Indefinite 'ein, ei, and eit' being before the word, and definite '-en -i -a -et' being added to the end.
Keep in mind that the vowel E at the end of kyrkj e and epl e are replaced completely by the suffix.