For alternate uses, see Q (disambiguation).

Q is the seventeenth letter of the Latin alphabet.

The Semitic sound value of Qôp was /q/. In Greek this sign (called Qoppa in Greek) probably came to represent several labial plosives, among them /k_w/ and /k_w_h/. These sounds changed to /p/ and /p_h/ respectively. Therefore, Qoppa was transformed into two letters: Qoppa, which stood for a number only, and Φι (Phi) which stood for the aspirated sound /p_h/ that came to be pronounced /f/ in Modern Greek. The Etruscans used Q only in conjunction with V, symbolizing thus a /k_w/. and V. Some scholars claim that Q and Phi are unrelated.

In most Modern Languages, Q is rather superfluous; in Romance and Germanic languages it usually appears followed by the letter u. In English this most often denotes the affricate /kw/, as it does in Italian; in German, /kv/; and in French, Spanish, and Catalan, /k/. (In Spanish, "qu" replaces c for /k/ before the vowels i and e, since in those contexts c is a fricative.). In Azeri, Uzbek, Tatar languages Q is pronounced the same as the Semitic sound q.

Quebec represents the letter Q in the NATO phonetic alphabet.

Q is:

• An abbreviation for 'Question'.
• A character in the James Bond series, see Q (James Bond).
• A character in the Star Trek series, see Q (Star Trek).
• The leading character in the famous Chinese novel A True Story of Ah Q by Lu Xun. Because of this novel, "Ah Q" in China means someone who always claims spiritual victory despite frequent defeat.
• The name of a bacterial infection, see Q fever.
• A name for anti-submarine ships, see Q-ship.
• The pen name of writer Arthur Quiller-Couch.
• The abbreviation used by scholars of the New Testament to describe the Q document, a hypothetical lost written "Source" (German, Quelle, hence, Q) behind the Synoptic Gospels.
• The stock symbol for Qwest Communications International Inc
• A bold Q is used by mathematicians to denote the set of rational numbers.
• In engineering, a symbol for characterizing filters, see Q factor.
• In physics, a symbol for electric charge.
• An "equational programming language"; see Q programming language.

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