As a Noun:
1. The present time of talking, writing or signing and not some other time. English = present.
2. The day on which or during which you are speaking, writing or signing. English = today, this day.
3. On the very day which has already been identified (in the future or in the past) on which other actions also happen. English = that day, on that day, on that very day.
As a Verb or Adjective:
1. To be people or things that exist now, rather than those that existed in the past or those that may exist in the future. English = (be) present, (be) current.
2. Used immediately next to a sign which names a period of time ('morning', 'afternoon', 'night', 'year' etc.) to mean one of those periods of time which is happening now or closest to you. English = 'this morning', etc.
As Modifier:
1. Used at the beginning of a sentence or immediately next to a verb to mean the action takes place at the time of talking, writing or signing and not some other time. English = now, at present, presently, currently, at the moment.
2. Used at the beginning, end, or beginning and end of a sentence, or immediately next to a verb to mean the action takes place on the day when you are signing, talking or writing. English = today, on this day.
3. Used at the beginning, end, or beginning and end of a sentence, or immediately next to a verb to mean the action takes place on a day you have already located. English = on that day, at that time.
4. Used at the beginning of a sentence to mean the action takes place or the situation exists at this time in history. English = nowadays.