Originally posted by Xneb https://forum.duolingo.com/comment/6279406
I have seen a lot of people seem to be confused as to which ending to use for the plural of a word. There is a lot to go through, but I'll try and simplify it as much as I can. The examples I have taken come from Danish: An Essential Grammar, however some I've altered to words I know are in the course.
-
Monosyllabic n-words ending in a consonant: add -e. For example:
En hund -> To hunde
En fugl -> To fugle
-
Polysyllabic nouns: add -(e)r. For example:
En pige -> To piger
En regning -> To regninger
If final vowel is stressed, add -er
En by -> To byer
Et træ -> To træer -
Ending in -dom: add -me. For example:
En ejendom -> To ejendomme
-
Ending in unstressed -er: add -e. For example:
En dansker -> To danskere
-
Ending in -hed, -i and -ion: add -er. For example:
En lejlighed -> To lejligheder
Et konditori -> To konditorier
En station -> To stationer
-
Ending in -skab when -skab isn't used in a literal sense: add -er. For example:
Et landskab -> To landskaber, however;
Et køkkenskab -> To køkkenskabe
-
Ending in -um: drop -um and add er. For example:
Et museum -> To museer
-
Ending in -el, -en and -er: swap e and consonant and add sometimes add -r. For example:
En kartoffel -> To kartofler
En tallerken -> To tallerkner or To tallerkener
Et eksempel -> To eksempler
En fader -> To fædre
Et nummer -> To numre
-
With short stressed vowel and single consonant: double consonant and add -e(r). For example:
En bus -> To busser
En hat -> To hatte -
Some loanwords also have their own special endings, relating to the original language. For example:
Et faktum -> To fakta
En muffin -> To muffins
-
Sometimes, both Danish or original language endings are possible, but these tend to be exclusively for English loanwords. For example:
En cowboy -> To cowboys or To cowboyer
-
However, more often than not, Danish will add its own inflections, or it will be a zero plural. For example:
Et drama -> To dramaer
En baby -> To babyer
En film -> To film
Hopefully that covers enough to help you guess the ending, but remember (and a bit of a disclaimer here) there are many many exceptions and irregular nouns (such as En sko -> To sko, En mand -> To mænd, En and -> To ænder). Best of luck, and hopefully this has formatted correctly so you can understand it.
N 
C1 
B2 
B1 
A1