I just had a weekend where I got to teach 4 players keyforge. These players were aware of the game, but none of them had read the rulebook. I did not have a printed copy of the rulebook, so I needed to explain the game verbally. I provided all of the decks. All players involved are very experienced gamers. The new players attempted to make couple mistakes several times, and several of them had to do with the words the game chose to use. Here is a list. I am going to provide suggestions for better words, but I understand how difficult this would be to change at this point.
1) Use - The easiest way to describe this is that the word "use" has too much baggage already associated with it. I specifically called this one out in advance as something that might confuse you, but even that didn't stop them from interpreting the cards wrong. "Activate" is the first word that comes to mind that could have prevented this.
2) Fight - "fight" vs "fighting" vs "a fight" required clarification often. I think this could have been solved by using the word "Attack" for "fight", and then have "fight" mean the same thing as "fighting"
3) Action - Because the first left aligned word on most artifacts is "Action", and because action cards exist, most people wanted to play artifacts as actions. I have noticed that I don't actually think of action cards as action cards when I look at them. I just see them as a non-creature whose only ability is a play ability. I think this would most easily be fixed with card layout, but using the same keyword twice was probably a bad plan, and changing either would probably fix the issue.