Dictionary.com Word FAQs
How do I figure out the plural form if it is not listed in the dictionary? How do I write the plural form of a compound noun if it is not listed in the dictionary?
For regular plurals and other inflections, most dictionaries do not explicitly offer all the forms - except for children's dictionaries. This is where reading the Guide or Introduction to your dictionary is very important. There should be a section in your dictionary about inflected forms. This is your guide to figuring out plurals and other inflections. English actually does not have that many inflected forms, compared to other languages. The plurals of nouns, the principal parts of verbs (past tense, past participle when it differs from past tense, present participle), and the comparative and superlative forms of adjectives and adverbs are often not given explicitly in dictionaries. In general, -s or -es is added to nouns for plurals, -ed and -ing are the verb endings, and -er and -est are the comparative and superlative forms. The inflected form(s) of regular words are not shown for one reason only - to save space in the dictionary for word information more likely to be sought. Inflected forms are also not shown at undefined run-ons that are regular. However, if the inflected form of a word is created in an irregular way or the dictionary user is likely to feel some doubt about the form, then the dictionary usually gives the full plural form (n, pl shampoos) or a cut-back version (n, pl -ties) is printed. For a compound word not listed in the dictionary, one should look up the second part of the construction and see how it is made into a plural, e.g., "reference book" would not have a dictionary entry, so you need to know the plurals of the individual words "reference" and "book."