I just wanna for saying 1 sentences with your listing. " bitcoin can make you rich just for a short time" I guess with sentences are containing a hyperbola can make the other people are feeling curious for let know about the bitcoin.

a scarce currency without a central bank. only you hold it. you move/secure it when & how you want

Hmmm. How about, "Online money, can be converted to virtually any currency and has high value."  I think when describing Bitcoin to friends, you don't really have to go into so much detail. Tell them enough to keep things interesting.

"A best way to earn extra money which will keep on growing over a period of time" and I am sure many of them will become curious to know more about it as everyone loves money 

"you are too late"

I think I choose" bitcoin is the cash of our society" because I believe bitcoin gives every one even child or older to opportunity to earn extra income even you are at home only. You can  make money because of that. And bitcoin are for the whole world. Any country you are  , age and gender you are always welcome to the bitcoin world.

Taking people by their greedyness is the best solution. Tell them that earlier they will enter and more patient they will be, richer they will end. A 100% working technic.

It is beter than Western Union, the transaction fees are really lower than what they offer and it dont go up that large even if you send a higher amount.

That will be my introduction and I think he will have questions after that.

This sentence which always used to introduce bitcoin to my friends
"A digital currency that gives you a chance to earn some real money that can be used to almost anything"
They interested immediately, then they curious how to get it

Bitcoin is a revolutionary technology that had introduced a new form of digital cryptocurrency currency which can be made one's computer or any mining system. Bitcoin have lot of advantages like it's fast and it's transaction fees is very low and we can earn Nixon easily with little effort