A word that means, be of use would be; helpful, useful, needed
Recycle is a word that means to use again.
The word that means unfair use of government power is "tyranny."
when you use the word "excuse you" it means you offended the person and there upset
There is no single word that means what you are looking for.
utilize
Colloquial.
mean
work
"The word peril means danger."
You may use the word 'sakebu.'
Some people use the word dear.
The word you are looking for is "reserve."