Answer:
Two in a whole and four in a pair. And six in a trio you see. And eight's a quartet but what you must get. Is the name that fits just one of me?
Through its wounds, water does run. It once held many but now has none. What is it?
You can read it both ways, I wearΝΎ One way it's a number, reversed a snare.
Round as a button, deep as a well. If you want me to talk, you must first pull my tail.
This is in a realm of true and in a realm false, but you experience me as you turn and toss.
When you take away the whole from me there is always some left.