Plural nouns and the rule that a syllable never ends in a double vowel
As you will see later, the plural for a noun is usually formed by adding _-en_ after the singular noun.
Let us consider the word _maan_ (moon).
To form the plural, we add _-en_: maanen
If we break it up into [syllables](#/lesson/SpellingAndPronunciation.04), we get: maa-nen
Following the rule about [double vowels at the end of a syllable](#/lesson/SpellingAndPronunciation.11), we are not allowed to have the syllable end in double _aa_.
The reason for this is that a syllable that ends in _one a_ is already considered to be a long-vowel syllable (recall that a
[short vowel](#/lesson/SpellingAndPronunciation.13) syllable always ends in a consonant).
The second _a_ is thus redundant: we will simply omit the second _a_.
ma ~~a~~ nen --> ma-nen --> manen
Keeping a long vowel word long
Suppose we do the exact opposite: we have a long vowel plural noun, and we have to turn it into a singular noun.
Let us take the plural noun stenen (stones).
The first syllable has a long vowel, for if we divide the word into its [syllables](#/lesson/SpellingAndPronunciation.04), we find that the first syllable ends in a vowel (e):
stenen
To derive a singular noun from a plural, we need to subtract _-en_:
sten
Now, the syllable ends in a [consonant](#/lesson/SpellingAndPronunciation.22) (n). We know by now that if a syllable has a single vowel and ends in a consonant, the vowel is a [short](#/lesson/SpellingAndPronunciation.13) one.
The plural noun was, however, a long vowel word, which generally means that the singular should be long too.
In order to keep the singular noun long, we have to add an extra vowel:
steen
Recall that all [double vowels](#/lesson/SpellingAndPronunciation.10) are long vowels.