1. If the noun ends in “y”, change it to “i” and add “es.” Example: company; companies.

2. Nouns ending in “o” preceded by a consonant is formed into a plural

by adding “es.” Example: hero; heroes.

3. Nouns ending in “f” become plural by changing “f” to “ves.” Example: calf; calves.

4. Certain nouns change a vowel sound when they become plural. Example: goose, geese; man, men; mouse, mice; and tooth, teeth. …

Regular plurals The plural morpheme in English is suffixed to the end of most nouns. The plural form is usually represented orthographically by adding -s to the singular form (see exceptions below). The phonetic form of the plural morpheme is [z] by default. Examples: boy -boys girl -girls chair -chairs When the preceding sound is a voiceless consonant—such as [t], [p], or [k]—it is pronounced [s]. Examples: cat -cats lap -laps clock -clocks Where a noun ends in a sibilant sound—[s], [z], or [ʤ]—the plural is formed by adding [ɪz] (also pronounced [əz]), which is spelled -es if the word does not already end with -e: dish -dishes glass -glasses judge -judges phase -phases witch -witches Morphophonetically, these rules are sufficient to describe most English plurals. However, there are several complications introduced in spelling. The -oes rule: most nouns ending in o preceded by a consonant also form their plurals by adding -es (pronounced [z]): hero -heroes potato -potatoes volcano -volcanoes or volcanos The -ies rule: nouns ending in a y preceded by a consonant usually drop the y and add -ies (pronounced [iz]). This is taught to many American and British students with the rhyme: “Change the y to i and add es”: cherry -cherries lady -ladies However, proper nouns (particularly those for people or places) ending in a y preceded by a consonant form their plurals regularly [1][2]: Germany Germanys (as in The two Germanys were unified in 1990; this rule is commonly not adhered to as several book titles show,[3][4] and Sicilies rather than Sicilys is the standard plural of Sicily) Harry Harrys (as in There are three Harrys in our office) The rule does not apply to words that are merely capitalized common nouns: P&O Ferries (from ferry) Other exceptions include lay-bys and stand-bys. Words ending in a y preceded by a vowel form their plurals regularly: day -days monkey -monkeys (Money/Monies is an exception, but money can also form its plural regularly.) To understand it. click this websites..thank you

The rule is add s – its the exceptions that are the problem.

Soupkitty has it summed up well for you so I won’t try adding to it