I've chosen "rhythm" as a medium-difficulty word for Hangman. This 6-letter word is particularly interesting because it contains no traditional vowels (a, e, i, o, u), only using 'y' as a vowel sound. This creates a good challenge for the player as they might initially focus on guessing common vowels, which won't appear in this word. It's a real English word that refers to a pattern of sound or movement, and it follows all the required rules: it's between 4-10 letters, uses only a-z, contains no spaces/hyphens/special characters, and is not a proper noun or acronym.