A modern common word to use in place of hitherto is "before", or one may choose to use "before now".

Thankyou both of you. If you don't mind, can you please tell me what is the best and common word that can be used as a substitute for hitherto?

Jade is correct..."hitherto" is rarely used in common conversation now, but you'll see it in older books, and sometimes in modern academic or legal texts.

Hitherto, I didn't use to use the word "hitherto." He was hitherto a bad person, but now he chooses to become a good person. We have solved hundreds of criminal cases hitherto. Overall, you did very well. But the truth is that "hitherto" is an older word that is almost never used in America anymore. However, it's a good word to know if you are reading a book that was written many years ago.