To form the simple present tense, the helping verb (auxiliary) “do” is usually used in front of the base or main verb. There are a few exceptions. Positive sentences do not generally require the helping verb. When the subject is in the third person and singular, “s” is either added to the main verb or “es” is added to the helping verb. The last exception is when “state of being” verbs are used (“to be” verbs), where the helping verb is omitted. This is true even in questions and negative sentences. The simple present tense is used to show general actions, actions that are habitual or occur in the past, present and future and statements that always hold true. This tense is also used in conditional (if) sentences. Consider the following examples:
Example 1: She drinks diet soda (positive sentence in 3rd person singular with a habitual action).
Example 2: She does not drink diet soda (negative sentence, helping verb has “es” added).
Example 3: She lives in Arizona (applies to the past, present and future).
Example 4: Sarah is at the store (“is” is a “state of being” verb, and the action is happening now).