?

Etymology
? may derive from Qo, with the Q written over the o, an abbreviation of Latin, placed at the end of a question to mark it as such.

Punctuation mark

 * Character #1: "I have no time to explain! Have you seen a Big Bad Wolf blowing down various houses?"
 * Character #2: "?"
 * Character #1: "I have no time to explain! Have you seen a Big Bad Wolf blowing down various houses?"
 * Character #2: "?"

Symbol

 * 1) A placeholder for an unknown word, phrase, text, or numerical value.
 * 2)  Indicator of a bad move.
 * 3)  A wildcard for one character in query language.
 * 4)  The ternary operator in some programming languages.
 * 5)  Detects zero or one occurrences of the preceding element.
 * The string  matches both "color" and "colour".
 * 1)  In a URL, begins a query string (a series of data formatted as field-value pairs).
 * 
 * 

Usage notes

 * Its English name is variously question mark, interrogation mark, interrogation point, eroteme.

Noun

 * 1)  A question.
 * i hav a ? 4 u (I have a question for you)
 * 1) objects seen/shaped as the question mark
 * a ? block (a question-mark block)

Punctuation mark

 * 1) Used in ¿ ?
 * 2)  Marks a preceding passage as a question, without the starting ¿, as in English and other languages

Usage notes

 * As SMS messaging and other forms of electronic communication have become more common, some Spanish-speakers use only ? for questions and ! for exclamations, leaving out the initial typographical mark. This is considered non-standard usage.