-eren
There are a few nouns to which we have to add -eren instead of -en:
| het kind
| de kinderen
| the child(ren)
|
| het kalf
| de kalveren
| the calves
|
| het ei
| de eieren
| the eggs
|
| het gemoed
| de gemoederen
| the moods
|
| het goed
| de goederen
| the goods
|
| het lam
| de lammeren
| the lambs
|
| het lied
| de liederen
| the songs
|
| het rund
| de runderen
| the oxen
|
| het volk
| de volkeren
| the peoples
|
Note the doubled 'm' in lammeren (see keeping vowels short) and the f that turned into v in kalveren (see hard and soft consonants).
The noun 'het been' gets an extra d:
| het been
| de beenderen
| the bones
|
'Been' has two different meanings: 1. bone and 2. leg. If it refers to a leg, the noun has a regular plural:
| het been
| de benen
| the legs
|
'Het blad' is irregular because we let the short vowel in the singular turn into a long one in the plural. The plural's syllables are separated by dashes so that you can see that the letter a is now a single open vowel. The regular spelling rules dictate that the d be doubled to keep the vowel short.
| het blad
| de bla-de-ren
| the leaves
|
| het blad
| de bla-den
| the sheets (of paper)
|
Both plurals are irregular. The regular plural form would have been bladden.
-a
Latin nouns that end in -um get -s in the plural. Some nouns can also take -a instead of s. The -a ending comes in the place of -um.
| het museum
| de museums / musea
| the museums
|
| het stadium
| de stadiums / stadia
| the phases
|
| het podium
| de podiums / podia
| the (theater) stages
|
| het aquarium
| de aquariums / aquaria
| the aquariums
|
The same can happen to words that end in -on, a less common ending in Dutch.
| het stadion
| de stadions / stadia
| the stadions
|
Questions? 
