adverb, noun which may take the genitive case particle 'no'
many times; time and time again; repeatedly
Used to emphasize that an action or event has occurred many times, often with a nuance of persistence or frequency. Can modify verbs directly as an adverb or nouns with の.
See also: 何度も (なんども)
I've warned him many times, but he never listens.
この映画は何回も見たくなる。
This movie makes you want to watch it again and again.
I've explained it many times, but he still doesn't understand.
I keep making the same mistake over and over again.
After overcoming many failures, I finally succeeded.
たびたび is a more formal or literary way to say 'frequently/repeatedly,' whereas 何回も is plain, everyday speech.
しばしば is a bookish, written-style synonym for 'often/repeatedly,' while 何回も is the natural spoken equivalent.
何回も describes something happening many times, while たまに describes something happening only occasionally.
Compound of 何 (nan, 'what') + 回 (kai, 'times') + も (mo, 'also/even'), literally 'even what number of times', used to mean 'many times'.