The word at the end of 1) s/x/ch/sh plus es.

Such as: classes, boxes, watches, brushes, foxes, matches, glasses,

2) For the words ending in "consonant +y", after changing Y to I, add es.

Such as: cities, countries, studies,

3) Add ES to the following O-ending words: Tomatoes, Potatoes, Heroes, Mangoes, ...

4) Some O-endings only add s: photos.