What are the 30 rules in forming plural nouns?

A plural noun is a word for two or more people, places, or things. Here are some rules to make singular nouns into plural nouns:

  • To make most nouns plural, add an s or es to the end of the word. These are called regular plurals (or regular nouns). Example: the plural of neighbor is neighbors, the plural of flower is flowers.
  • Nouns ending in s, z, ch, sh, or x, add es to the end of the word to make it plural. The plural of dish is dishes.
  • Some nouns ending with o are pluralized by adding and es to the end of the word. The plural of tomato is tomatoes.
  • Most nouns ending with o are pluralized by adding s to the end of the word. The plural of photo is photos.
  • Nouns that form their plural in some other way are called irregular plural (or irregular nouns). Example: the plural of child is children, the plural of foot is feet.
  • When a noun ends in a y, change the y at the end of the word to an ies. The plural of berry is berries.
  • Some nouns ending with y, preceded by a vowel, are pluralized by just adding s to the end of the word. The plural of day is days.
  • Nouns ending with f or fe, change to f or the fe to ves to form the plural. The plural of life is lives.
  • Nouns ending with ff are usually pluralized by just adding an s to the end of the word. The plural of cuff is cuffs.
  • Some nouns change the vowel sound to become plural. The plural of man is men, the plural of tooth is teeth.
  • Some Old English plurals are still in use. The plural of child is children, the plural of ox is oxen.
  • Some nouns that end with is, the ending is changed to es to form the plural. The plural of crisis is crises.
  • Some nouns that end with um, the um is replaced with an a. The plural for datum is data, the plural for medium is media.
  • Some nouns that end with on, the on is replaced with an a. The plural of phenomenon is phenomena.
  • Some nouns that end is a, change the a at the end of the word to ae. The plural of larva is larvae.
  • Some nouns that end in ex or ix, the plural is formed by changing the x to ces. The plural of index is indeces, the plural of matrix is matrices.
  • Some nouns that end in us, the plural is formed by changing the us to i. The plural of cactus is cacti, the plural of radius is radii.
  • Nouns ending in eau, the plural is formed by adding x to the end of the word. The plural of bureau is bureaux.
  • There are any number of other variations such as the plural of tempo is tempi; the plural of cherub is cherubim; the plural of person is people. But language evolves over time or we would still be speaking like Shakespeare.
  • Even as I type these rules, some are officially amended. For example, the plural forms indeces and indexes are both being accepted as correct plurals for index and the plural forms; bureaux and bureaus are both being accepted as correct plurals for bureau, as are many other irregular plurals being found in standard dictionaries with modernized plural options.