How do singular nouns that end in y preceded by a vowel form their plural?

Singular nouns that end in "y" preceded by a vowel form their plural by simply adding an "s".

Here are some examples:

* boy - boys

* toy - toys

* monkey - monkeys

* valley - valleys

* attorney - attorneys

This is because the "y" isn't the final consonant in these words; it's the vowel that dictates the plural formation.