A chinese word meaning sharp knife. It is an added letter to mean "sharpened" in "sword".
In order for the sword to function, it must always be sharp and pointed. That way you can defeat the enemy in a timely manner. However, if the blade is dull and rust-rusted, it is a scrap metal sculpture.
This is also the capacity of man. If you do not put your ability in the ready state like a sword blade, you will not be able to catch it when it comes. The chance of life goes by in a moment and we must be like a pointed sword to catch it.