today (Noun) — The day that includes the present moment (as opposed to yesterday or tomorrow). ex. "Today is beautiful" ex. "did you see today's newspaper?"
today (Noun) — The present time or age. ex. "the world of today" ex. "today we have computers"
today (Adverb) — In these times. ex. "today almost every home has television"
today (Adverb) — On this day as distinct from yesterday or tomorrow. ex. "I can't meet with you today"