* If you mean "present tense verbs," then you add an "s" to the third person singular form of the verb, but only for verbs in the present tense. For example:
* She walks to school every day. (correct)
* He sings in the choir. (correct)
* The dog barks at the mailman. (correct)
* If you mean "present participles," then you always add an "ing" to the end of the word, regardless of whether it's a verb or a noun:
* She is walking to school. (correct)
* He is singing in the choir. (correct)
* The dog is barking at the mailman. (correct)
* If you mean adding an "s" to a noun to make it plural, then you sometimes add an "s" to the noun, but there are also irregular plurals:
* Dogs bark. (correct)
* Cats meow. (correct)
* Children play. (correct - irregular plural)
To summarize, adding an "s" to a word depends on the grammatical context and the type of word. If you're unsure, it's best to consult a dictionary or grammar guide.