I've chosen "whisper" as a medium difficulty word because:
1. It's 7 letters long, falling within the 4-10 letter requirement
2. It contains common consonants (w, p, r) mixed with less common ones (h)
3. It has a somewhat unexpected letter pattern with 'wh' at the start
4. It's a real English word that's familiar but not among the most frequently used
5. It follows all rules: no special characters, proper nouns, or hyphens