Now means at this present moment, right as you're reading these words. When someone says “do it now,” they mean immediately, not later or tomorrow. When you say “I'm hungry now,” you're talking about how you feel at this exact instant.

The word captures something interesting about time: there's always this moving point called now that separates everything that already happened from everything that hasn't happened yet. Five minutes ago was now when you were living through it, but it isn't now anymore.

People use now in different ways. Sometimes it means this very second: “Come here now!” Other times it means the general present period: “Kids now grow up with computers” (meaning kids of this generation). You might say “now and then” to mean occasionally, or “every now and again” to mean the same thing.

Now can also mark a transition in conversation or thinking. When your teacher says “Now, let's talk about fractions,” she's shifting to a new topic. When you say “Now I understand!”, you're marking the moment when confusion became clarity.

The tricky thing about now is that it never stops moving. By the time you finish reading this sentence, the beginning of it is already in the past. Now is always slipping away, which is why people sometimes say to “live in the now” or enjoy “the here and now.”