* 後 (あと) - ato: This is the most common and general word for "after," meaning "afterwards" or "later." It's used for time. Example: 会議の後 (kaigi no ato) - after the meeting.
* 後で (あとで) - ato de: This is also very common and means "later" or "afterwards," often implying a slightly more definite time than just "ato." Example: 後で電話します (ato de denwa shimasu) - I'll call later.
* 〜の後で (〜のあとで) - ~ no ato de: This is a more formal way to say "after ~." You replace the "~" with the noun. Example: 食事の後で (shokuji no ato de) - after the meal.
* 以降 (いこう) - ikō: This means "after" in the sense of "from then on" or "following." It refers to a point in time and everything that comes after. Example: 10時以降 (jū-ji ikō) - after 10 o'clock.
* 〜してから (〜してからは) - ~ shite kara / ~ shite kara wa: This means "after doing ~" or "after ~ has happened." You replace the "~" with the verb. Example: ご飯を食べた後 (gohan o tabeta ato) - after eating a meal. This is very common and often preferred to just using "ato."
Which word is most appropriate depends entirely on the sentence. Provide a sentence and I can help you choose the best translation.