What an interesting sentence! Native speakers will make the (correct) assumption that the knight owns the sword. But technically, the sentence does leave open the possibility that the warrior owns the sword. In this example, it is only context which tells native speakers who owns the sword. Because it is a tool for killing, it makes the most sense for the knight to be using it. But if you use the exact same sentence structure with different context, then ownership can change. For example: "The knight kissed the woman with a blue purse." In this sentence, the context tells us that the woman owns the purse, because it is not a tool used for kissing. Here are some ways to make sure that this sentence defines ownership: 1) The knight used a sword to kill the warrior. 2) The knight killed the warrior, using a sword. 3) Using a sword, the knight killed the warrior. 4) The warrior was killed by the knight with a sword. (not recommended, as this is passive language)

From our knowledge of the world, we know that it would be surprising for a knight to kill the warrior with the warrior's own sword. If the writer meant that, the writer would need to say so explicitly: "The knight killed the warrior with the warrior's own sword." Since the writer doesn't say that, we are 99% certain that the knight owned the sword. In real life, the sentence is fine. As an exam question, perhaps, from the point of view of pure grammar and logic, and with no other context, no, we don't know absolutely for sure. Pearl Webster's wording, "The knight used his sword to kill the warrior" makes it completely clear. Darryl Wee's, wording, "The knight killed the warrior with his sword" is still not completely clear because we can't be absolutely sure which person the word "his" refers to.

Most definitely the knight has the sword. The key words are "killed" and "with a sword", so without any other information the knight is most likely the owner. If you really want to make the knight the sword's owner, just say "The knight killed the warrior with his/her sword". To take it even further, I think it would be very unlikely the warrior fell on his own sword and the knight just stood by and watched.

Corrections: 1. Can you from this sentence clearly define who owns the sword? = Can you clearly define from this sentence who owns the sword? 2.How can I change the sentence to know for sure whose it is the sword? = How can I change the sentence to know for sure whose sword it is? No, from the sentence you cannot be sure about who owns the sword. You could say e.g: The knight seized the warrior's sword and killed him with it. The knight raised his sword high and killed the warrior.

Hi Edward, We cannot tell with certainty the owner of the sword. We do not see words such as "his", "her" or "their" to indicate any possible possession. Therefore, if we want to describe with certainty, we can say: The knight killed the warrior with his sword. With his sword, the knight killed the warrior. Just for fun, imagine the knight killed the warrior with the warrior's own sword. The knight killed the warrior with the latter's sword. Hope this helps. Cheers, Lance