今日 vs 本日 (today)
Whats the difference between 今日 kyou and 本日 honjitsu, both meaning today. I've been taught 今日 but rarely 本日. Is 今日 more commonly used than 本日, and when should you use 本日? They both mean today, so why are their two words for the same thing?
本日 is keigo. It is the polite formal Japanese you will hear all the time when listening to an announcement on a train, airplane, or in a store in Japan. You will likely hear it, so it's good to know. But you will likely not be using it much (unless you're making formal announcement in Japan for some reason).
今日 is what you typically will say and hear in everyday situations.
本日 may be a little more polite, and may be more used in newspapers, documents. You can use both of them, no problem at all.
There are many synonyms, words that has the same meanings in every languages, it also applies to Japanese. For example, 教師 and 先生, both mean 'teacher' and there is no real reason (well there is maybe one) why there are two words with the same meaning.
This is the usage example for each. 本日はお越しいただきありがとうございます。 honjitu ha okoshi itadaki arigatou gozaimasu. 今日は 来てくれて ありがとう！ kyou ha kite kurete arigatou!