In English grammar, we do not form the simple past tense by adding "s" to the end of the verb. The simple past tense is formed differently depending on the verb. Regular verbs typically add "-ed" to the base form of the verb to form the simple past tense, while irregular verbs have their own unique forms in the past tense. For example, the regular verb "walk" becomes "walked" in the simple past tense, while the irregular verb "go" becomes "went" in the simple past tense.