Nominative singular and plural of masculine nouns
Most masculine nouns take the ending -ы or -и in the nominative plural. They take the ending -и, when the singular ends with -й -ь -г -ж -к -х -ч -ш or -щ. Some common masculine nouns take the ending -a or -я. Sometimes, if the nominative singular ends in -ь, this is replaced by -я in the plural.