The document discusses rules for modifying verbs in English. It provides examples of adding "s" to verbs to make them third person singular in present tense, such as "plays", "cries", and "flies". It also provides examples of changing the ending of verbs ending in "ch", "o", "x", "sh", "ss", and "z" such as "watches" and "buzzes". Finally, it discusses how the verbs "have", "do", and "go" are modified with an "s" when making them third person singular.