New learning.
I just noticed this in the advertising section of the forum.
The Bitcoin software, network, and concept is called "Bitcoin" with a capitalized "B". Bitcoin currency units are called "bitcoins" with a lowercase "b" -- this is often abbreviated BTC.
Image:
http://prntscr.com/mblnlfMeaning when I am paying someone in
Bitcoin then I am sending him
bitcoins 
We are
Bitcoiners and
bitcoins are our currency.
Yes, coins (currency) are low case, unless its the beginning of a sentence. This is easier to remember in countries that use someone's name as the coin name, because you remember that unless you are referring to the person, you have to use low case.
That is why you are supposed to say US dollar and not Dollar. But of course we have the symbol ₿ (
BTC) just like the dollar has $, the euro , the pound sterling £, etc.
Example: In the Euro zone, they use the euro () as currency.
Or: "If I could get 1 satoshi for every time someone mentioned Satoshi, I would be rich!"
Just my two satoshis...