In logic and related fields such as mathematics and philosophy, "if and only if" is a biconditional logical connective between statements, where either both statements are true or both are false. The connective is biconditional, and can be likened to the standard material conditional combined with its reverse ("if"); hence the name. The result is that the truth of either one of the connected statements requires the truth of the other, though it is controversial whether the connective thus defined is properly rendered by the English "if and only if"—with its pre-existing meaning. For example, P if and only if Q means that P is true whenever Q is true, and the only case in which P is true is if Q is also true, whereas in the case of P if Q, there could be other scenarios where P is true and Q is false.
Propositional calculus is a branch of logic. It is also called propositional logic, statement logic, sentential calculus, sentential logic, or sometimes zeroth-order logic. It deals with propositions and relations between propositions, including the construction of arguments based on them. Compound propositions are formed by connecting propositions by logical connectives. Propositions that contain no logical connectives are called atomic propositions.
Q, or q, is the 17th letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is pronounced, most commonly spelled cue, but also kew, kue and que.
RSA (Rivest–Shamir–Adleman) is a public-key cryptosystem, one of the oldest widely used for secure data transmission. The initialism "RSA" comes from the surnames of Ron Rivest, Adi Shamir and Leonard Adleman, who publicly described the algorithm in 1977. An equivalent system was developed secretly in 1973 at Government Communications Headquarters (GCHQ), the British signals intelligence agency, by the English mathematician Clifford Cocks. That system was declassified in 1997.
Q is a fictional character, as well as the name of a race, in Star Trek, appearing in the Next Generation, Deep Space Nine, Voyager, Lower Decks, and Picard series and in related media. The most familiar Q is portrayed by John de Lancie. He is an extra-dimensional being of unknown origin who possesses immeasurable power over time, space, the laws of physics, and reality itself, being capable of altering it to his whim. Despite his vast knowledge and experience spanning untold eons, he is not above practical jokes for his own personal amusement, for a Machiavellian or manipulative purpose, or to prove a point. He is said to be almost completely omnipotent and he is continually evasive regarding his true motivations.
In statistics, the standard deviation is a measure of the amount of variation of a random variable expected about its mean. A low standard deviation indicates that the values tend to be close to the mean of the set, while a high standard deviation indicates that the values are spread out over a wider range.
An electric field is the physical field that surrounds electrically charged particles. Charged particles exert attractive forces on each other when their charges are opposite, and repulsion forces on each other when their charges are the same. Because these forces are exerted mutually, 2 charges must be present for the forces to take place. The electric field of a single charge describes their capacity to exert such forces on another charged object. These forces are described by Coulomb's Law, which says that the greater the magnitude of the charges, the greater the force, and the greater the distance between them, the weaker the force. Thus, we may informally say that the greater the charge of an object, the stronger its electric field. Similarly, the electric field is stronger nearer charged objects and weaker further away. Electric fields originate from electric charges and time-varying electric currents. Electric fields and magnetic fields are both manifestations of the electromagnetic field, one of the four fundamental forces of nature.
In mathematics, the quaternion number system extends the complex numbers. Quaternions were first described by the Irish mathematician William Rowan Hamilton in 1843 and applied to mechanics in three-dimensional space. The algebra of quaternions is often denoted by H, or in blackboard bold by Although multiplication of quaternions is noncommutative, it gives a definition of the quotient of two vectors in a three-dimensional space. Quaternions are generally represented in the form
2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and only even prime number. Because it forms the basis of a duality, it has religious and spiritual significance in many cultures.
Exclusive or or exclusive disjunction or exclusive alternation or logical non-equivalence or logical inequality is a logical operator whose negation is the logical biconditional. With two inputs, XOR is true if and only if the inputs differ. With multiple inputs, XOR is true if and only if the number of true inputs is odd.
Hamiltonian mechanics emerged in 1833 as a reformulation of Lagrangian mechanics. Introduced by Sir William Rowan Hamilton, Hamiltonian mechanics replaces (generalized) velocities used in Lagrangian mechanics with (generalized) momenta. Both theories provide interpretations of classical mechanics and describe the same physical phenomena.
Q is a popular music online magazine that was published monthly in the United Kingdom. It was first published in print from 1986 to 2020, it was inactive from 2020 until 2023. In 2023, Q was revived as an online publication. It was founded in 1986 by broadcast journalists Mark Ellen and David Hepworth, who were presenters of the BBC television music series The Old Grey Whistle Test. Q's final issue was published in July 2020, but began posting new articles to their website in 2023.
Kamaal Ibn John Fareed, better known by his stage name Q-Tip, is an American rapper, record producer, singer, and DJ. Nicknamed the Abstract, he is noted for his innovative jazz-influenced style of hip hop production and his philosophical, esoteric and introspective lyrical themes. He embarked on his music career in the late 1980s, as an MC and main producer of the influential alternative hip hop group A Tribe Called Quest. In the mid-1990s, he co-founded the production team The Ummah, followed by the release of his gold-certified solo debut Amplified in 1999. In the following decade, he released the Grammy Award-nominated album The Renaissance (2008) and the experimental album Kamaal the Abstract (2009).
In linear algebra, a rotation matrix is a transformation matrix that is used to perform a rotation in Euclidean space. For example, using the convention below, the matrix
QAnon is a far-right American political conspiracy theory and political movement which originated in 2017. QAnon centers on fabricated claims made by an anonymous individual or individuals known as "Q". Those claims have been relayed and developed by online communities and influencers. Their core belief is that a cabal of Satanic, cannibalistic child molesters are operating a global child sex trafficking ring which conspired against Donald Trump. QAnon has direct roots in Pizzagate, an Internet conspiracy theory that appeared one year earlier, but also incorporates elements of many other theories. QAnon has been described as a cult.
Margaret Denise Quigley, professionally known as Maggie Q, is an American actress, activist, and model.
In mathematics, a rational number is a number that can be expressed as the quotient or fraction of two integers, a numerator p and a non-zero denominator q. For example, is a rational number, as is every integer. The set of all rational numbers, also referred to as "the rationals", the field of rationals or the field of rational numbers is usually denoted by boldface Q, or blackboard bold
Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called electrostatic force or Coulomb force. Although the law was known earlier, it was first published in 1785 by French physicist Charles-Augustin de Coulomb. Coulomb's law was essential to the development of the theory of electromagnetism and maybe even its starting point, as it allowed meaningful discussions of the amount of electric charge in a particle.
The Q source (also called The Sayings Gospel, Q Gospel, Q document(s), or Q; from German: Quelle, meaning "source") is a hypothetical written collection of primarily Jesus' sayings (λόγια : logia). Q is part of the common material found in the Gospels of Matthew and Luke but not in the Gospel of Mark. According to this hypothesis, this material was drawn from the early Church's oral gospel traditions.
