You should be able to press the “ENTER” key or click on the “Fight!” button to submit a word.
If those aren’t working, it’s possible some game rule is preventing the submission.
- Words in your memory list (recently used) cannot be used again
- There’s a pretty limited English dictionary that the word must be in
- A word must be at least the minimum character length for your character’s minimum word stat
- Some enemies and player characters add other restrictions
Finally, if it’s not of these things, it could be a bug!