Unknown

"When the Question Mark Appears in the
Equation (eg; 1+? = 1), it Means there's an
Unknown Factor we Might Want to Identify.
When the Question Mark Appears alone,
(eg; ... = ?), it Signals that we Need to Find
Out what the ? Stands for. Either Way; a
Question Mark Tells us there's something
unknown. Something Unidentified."
- M4TH3M4T1C14N for TH3 64M3