Some of the masculine nouns in the group undergo a vowel modification, as do the only two feminine nouns in this group. The neuter nouns don't change. When the nouns in Table 3.15 become plural, they take the ending -e . The plurals of the nouns in Table 3.16 end in -er . Wherever possible, vowels are modified.
Compound nouns take the plural form of the last noun.
Because Arzt comes last, it is the only part of the compound noun that becomes plural. Always die Some nouns in German are used only in their plural forms. These are worth noting, particularly because you don't have to worry about whether the articles preceding them are masculine, feminine, or neuter. They always take the plural article die . A few nouns in German take an -s to form the plural.