By far most nouns take - _en_ in the plural. The formula is very simple:
noun + _en_
However, when you add - _en_ to a noun, you have to bear in mind three spelling rules:
1. Maintain the length of the vowel
Short vowels should stay short, long vowels should stay long, regardless of whether the noun is written in its singular or plural form.
See also [keeping vowels short/long](#/lesson/SpellingAndPronunciation.19).
de ro k | de ro kk en | the skirt(s)
het geva l | de geva ll en | the case(s)
2. No open double vowel
If the last syllable of the singular form contains a double vowel, be sure to avoid an 'open double vowel' in the plural form.
de p ee r | de p e ren | the pear(s)
het gev aa r | de gev a ren | the danger(s)
3. Replace hard f/s by soft v/z
If a singular noun ends in hard (unvoiced) _f_ or _s_, we generally write soft (voiced) _v_ and _z_ in the plural. See also [hard and soft consonants](#/lesson/SpellingAndPronunciation.23).
de neu s | de neu z en | the nose(s)
de brie f | de brie v en | the letter(s)