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Formal charges in ozone and the nitrate anion. In chemistry, a formal charge (F.C. or q*), in the covalent view of chemical bonding, is the hypothetical charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity.
The word "formal" indicates that the series need not converge. In mathematics, and especially in algebra, a formal series is an infinite sum that is considered independently from any notion of convergence and can be manipulated with algebraic operations on series (addition, subtraction, multiplication, division, partial sums, etc.).
A formal power series can be loosely thought of as an object that is like a polynomial, but with infinitely many terms.Alternatively, for those familiar with power series (or Taylor series), one may think of a formal power series as a power series in which we ignore questions of convergence by not assuming that the variable X denotes any numerical value (not even an unknown value).
Formal language, which is a set of well-formed formulas, which are strings of symbols from an alphabet, formed by a formal grammar (consisting of production rules or formation rules). Deductive system , deductive apparatus, or proof system , which has rules of inference that take axioms and infers theorems , both of which are part of the formal ...
A formality is an established procedure or set of specific behaviors and utterances, conceptually similar to a ritual although typically secular and less involved. A formality may be as simple as a handshake upon making new acquaintances in Western culture to the carefully defined procedure of bows, handshakes, formal greetings, and business card exchanges that may mark two businessmen being ...
An atomic formula is a formula that contains no logical connectives nor quantifiers, or equivalently a formula that has no strict subformulas. The precise form of atomic formulas depends on the formal system under consideration; for propositional logic, for example, the atomic formulas are the propositional variables.
In mathematical logic, a ground term of a formal system is a term that does not contain any variables. Similarly, a ground formula is a formula that does not contain any variables. In first-order logic with identity with constant symbols and , the sentence () is a
In logic and mathematics, a formal proof or derivation is a finite sequence of sentences (known as well-formed formulas when relating to formal language), each of which is an axiom, an assumption, or follows from the preceding sentences in the sequence, according to the rule of inference.