Are "friends" and "fellas" always interchangeable?
No, the words "fellas" and "friends" are not always interchangeable. "Fella" is a word meaning man and therefore can only really be used to refer to people who are male. Whereas the word friends is gender neutral and can be used for males and females. therefore, the only situation in which you can exchange friends for fellas is if you're speaking simply about men. Also, please note that the word "fella" is kind of old-fashioned and not very common these days. Ex: Guys, it's this fella's birthday. Ex: Are all the fellas coming?