Q is the seventeenth letter in the ISO basic Latin alphabet, following P and preceding R. It is also used as a symbol and abbreviation in various contexts.
As a Letter
- Pronunciation: In English, the name of the letter Q is pronounced /kjuː/.
- Origin and History: The letter Q originated from the Semitic letter Qoph (Qōp), which represented a sound likely similar to a velarized voiceless uvular stop /q/. The Greek letter Koppa (Ϙ) was derived from Qoph, and subsequently, the Etruscans and Romans adopted it. In Latin, Q was primarily used in the digraph "QU" to represent the labialized velar stop /kw/.
- Modern English Use: In modern English, 'Q' is almost invariably followed by 'U' (e.g., "queen," "quite," "quarry"). The "QU" combination typically represents the /kw/ sound, although it can represent /k/ in some words derived from French (e.g., "unique," "antique," "boutique"). Some rare exceptions where 'Q' is not followed by 'U' in English words include transliterations from other languages, such as "Qat" (a plant) or "Iraq," or in proper nouns like "Qantas."
- Other Languages: Its usage varies across languages. In some languages like Albanian, Maltese, and some Turkic languages, it represents a voiceless uvular stop /q/. In French, 'Q' can appear at the end of words without a 'U', often silent (e.g., "cinq").
As a Symbol or Abbreviation
Science and Technology:
- Physics:
- Electric Charge: Commonly used to denote electric charge (measured in coulombs, C).
- Heat: Represents heat energy transferred (measured in joules, J).
- Quality Factor: In resonant systems, 'Q' (or Q-factor) is a dimensionless parameter that describes how underdamped an oscillator or resonator is.
- Quantity: In general, it can denote quantity, particularly in equations.
- Chemistry:
- Glutamine: The single-letter code for the amino acid glutamine.
- Reaction Quotient: In chemical thermodynamics, Q is the reaction quotient.
- Mathematics:
- Rational Numbers: $\mathbb{Q}$ (blackboard bold Q) represents the set of rational numbers.
- Quaternions: Can represent the set of quaternions.
- Computing:
- Query: Often used to denote a query, as in Q&A or database queries.
- Queue: In data structures and algorithms, 'Q' can represent a queue.
Culture and Society:
- Literature and Media:
- Q Source: In biblical scholarship, the Q source (from German Quelle, meaning "source") is a hypothetical written collection of sayings of Jesus, believed by many scholars to have been used by Matthew and Luke.
- James Bond Character: Q, a fictional character in the James Bond series, who is the head of Q Branch (Quartermaster), the research and development division of the British Secret Service.
- Star Trek Character: Q, a powerful, god-like entity from the Star Trek universe.
- QAnon: A far-right conspiracy theory and political movement.
- Military and Intelligence:
- Q-ships: Heavily armed merchant ships with concealed weaponry, used to lure U-boats into an attack during World Wars.
- Q Clearance: A U.S. Department of Energy security clearance equivalent to Top Secret.
- Education:
- Question: Frequently used as an abbreviation for "question," especially in tests and questionnaires (e.g., Q1, Q2).
- Quarter: Can refer to a quarter of a year, especially in financial reporting (e.g., Q1 for first quarter).
- Phonetics: In the International Phonetic Alphabet (IPA), /q/ represents the voiceless uvular stop.
Other Uses:
- Finance: NASDAQ stock symbol for the Invesco QQQ Trust, an exchange-traded fund.
- Logic: Often used to represent a proposition, alongside 'P'.
- Chess: Abbreviation for Queen.
See Also
- Alphabet
- Latin alphabet
- Qoph
- Koppa