* Noun: This is the most common usage. It refers to the act of defending, a system of protection, or the people or things that defend.
* Example: "The team's strong defense led them to victory."
* Verb: This usage is less common. It means to protect or to argue in favor of something.
* Example: "The lawyer defensed his client against the accusations."
The context will usually make it clear which part of speech "defense" is.