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The colon, :, is a punctuation mark consisting of two equally sized dots aligned vertically. A colon often precedes an explanation, a list, [1] or a quoted sentence. [2] It is also used between hours and minutes in time, [1] between certain elements in medical journal citations, [3] between chapter and verse in Bible citations, [4] and, in the US, for salutations in business letters and other ...
Syntactically, (1) and (2) are derivable from each other via the rules of contraposition and double negation. Semantically, (1) and (2) are true in exactly the same models (interpretations, valuations); namely, those in which either Lisa is in Denmark is false or Lisa is in Europe is true. (Note that in this example, classical logic is assumed.
Another approach is to use with equal rights connectives of a certain convenient and functionally complete, but not minimal set. This approach requires more propositional axioms, and each equivalence between logical forms must be either an axiom or provable as a theorem. The situation, however, is more complicated in intuitionistic logic.
The triple bar character in Unicode is code point U+2261 ≡ IDENTICAL TO (≡, ≡). [1] The closely related code point U+2262 ≢ NOT IDENTICAL TO (≢, ≢) is the same symbol with a slash through it, indicating the negation of its mathematical meaning.
According to Florian Cajori in A History of Mathematical Notations, Johann Rahn used both the therefore and because signs to mean "therefore"; in the German edition of Teutsche Algebra (1659) the therefore sign was prevalent with the modern meaning, but in the 1668 English edition Rahn used the because sign more often to mean "therefore".
Punctuation in the English language helps the reader to understand a sentence through visual means other than just the letters of the alphabet. [1] English punctuation has two complementary aspects: phonological punctuation, linked to how the sentence can be read aloud, particularly to pausing; [2] and grammatical punctuation, linked to the structure of the sentence. [3]
The equals sign (British English) or equal sign (American English), also known as the equality sign, is the mathematical symbol =, which is used to indicate equality in some well-defined sense. [1] In an equation , it is placed between two expressions that have the same value, or for which one studies the conditions under which they have the ...
In English, when a quotation follows other writing on a line of text, a space precedes the opening quotation mark unless the preceding symbol, such as an em dash, requires that there be no space. When a quotation is followed by other writing on a line of text, a space follows the closing quotation mark unless it is immediately followed by other ...