post category link and password entry screen text

Hi. Is it possible to change the text for the post category link? (Example, bottom of https://wellnesswarriorsboston.org/2018/02/14/5103/) Is it possible to change the text of the password entry screen so we can say something like "Check your email for your password"? I have a feeling that this can only be done with a child theme, in which case I won't bother, but I am hopeful that I am wrong! Alice