Verbs tell time with a quality known as tense. Before you reach for a tranquilizer, here’s the lowdown on the basic tenses. The three basic tenses are past, present, and future, and each has two forms — low-carb and fat-free. Sorry, I mean plain (its basic time designation — present, past, or future) and progressive (the -ing form of a verb). Progressive places a little more emphasis on process or on action that spans a time period, and the present progressive may reach into the future. In many sentences either plain or progressive verbs may be used interchangeably. Here’s a taste of each: