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  2. Mind your Ps and Qs - Wikipedia

    en.wikipedia.org/wiki/Mind_your_Ps_and_Qs

    Movable type p's and q's could be easily mistaken, especially as they are mirror-reversed from the printed result. According to Michael Quinion, "investigations by the Oxford English Dictionary in 2007 when revising the entry turned up early examples of the use of Ps and Qs to mean learning the alphabet. The first is in a poem by Charles ...

  3. Necessity and sufficiency - Wikipedia

    en.wikipedia.org/wiki/Necessity_and_sufficiency

    The assertion that Q is necessary for P is colloquially equivalent to "P cannot be true unless Q is true" or "if Q is false, then P is false". [9] [1] By contraposition, this is the same thing as "whenever P is true, so is Q". The logical relation between P and Q is expressed as "if P, then Q" and denoted "PQ" (P implies Q).

  4. Disjunctive syllogism - Wikipedia

    en.wikipedia.org/wiki/Disjunctive_syllogism

    Equivalently, if P is true or Q is true and P is false, then Q is true. The name "disjunctive syllogism" derives from its being a syllogism, a three-step argument, and the use of a logical disjunction (any "or" statement.) For example, "P or Q" is a disjunction, where P and Q are called the statement's disjuncts.

  5. List of logic symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_logic_symbols

    definition: is defined as metalanguage:= means "from now on, is defined to be another name for ." This is a statement in the metalanguage, not the object language. The notation may occasionally be seen in physics, meaning the same as :=.

  6. Truth table - Wikipedia

    en.wikipedia.org/wiki/Truth_table

    A truth table is a mathematical table used in logic—specifically in connection with Boolean algebra, Boolean functions, and propositional calculus—which sets out the functional values of logical expressions on each of their functional arguments, that is, for each combination of values taken by their logical variables. [1]

  7. Logical equivalence - Wikipedia

    en.wikipedia.org/wiki/Logical_equivalence

    Logical equivalence is different from material equivalence. Formulas and are logically equivalent if and only if the statement of their material equivalence is a tautology.

  8. Apostrophe - Wikipedia

    en.wikipedia.org/wiki/Apostrophe

    APA style requires the use of italics instead of an apostrophe: ps, ns, etc. [70] In the phrase dos and don'ts , most modern style guides disparage spelling the first word as do's . However, there is a lack of consensus and certainly the use of an apostrophe continues, legitimately, in which "the apostrophe of plurality occurs in the first word ...

  9. If and only if - Wikipedia

    en.wikipedia.org/wiki/If_and_only_if

    In writing, phrases commonly used as alternatives to P "if and only if" Q include: Q is necessary and sufficient for P, for P it is necessary and sufficient that Q, P is equivalent (or materially equivalent) to Q (compare with material implication), P precisely if Q, P precisely (or exactly) when Q, P exactly in case Q, and P just in case Q. [3]