Formal

Formal, formality, informal or informality imply the complying with, or not complying with, some set theory of requirements (substantial form, in Ancient Greek). They may refer to:

• Formal wear, attire for formal events
• Semi-formal attire, attire for semi-formal events
• Informal attire, more controlled attire than casual but less than formal
• Formal (university), official university dinner, ball or other event
• School formal, official school dinner, ball or other event

• Formal logic, or symbolic logic
• Informal logic, the complement, whose definition and scope is contentious
• Formal fallacy, reasoning of invalid structure
• Informal fallacy, the complement
• Informal mathematics, also called naïve mathematics
• Formal cause, Aristotle's intrinsic, determining cause
• Formal power series, a generalization of power series without requiring convergence, used in combinatorics
• Formal calculation, a calculation which is systematic, but without a rigorous justification
• Formal set theory, as opposed to Naive set theory
• Formal derivative, an operation on elements of a polynomial ring which mimics the form of the derivative from calculus

• Formal methods, mathematically based techniques for the specification, development and verification of software and hardware systems
• Formal specification, describes what a system should do, not how it should do it
• Formal verification, proves correctness of a system

• Formal system, an abstract means of generating inferences in a formal language
• Formal language, comprising the symbolic "words" or "sentences" of a formal system
• Formal grammar, a grammar describing a formal language
• Colloquialism, the linguistic style used for informal communication
• T–V distinction, involving a distinction between formal and informal words for "you"
• Formal proof, a fully rigorous proof as is possible only in a formal system
• Dynamic and formal equivalence word-for-word translation, especially of the Bible

• Formal concentration, molar concentration of original chemical formula in solution
• Formal (pronounced "form-al")
• A compound CH₂(OR)₂, named in analogy to Acetal CHR¹(OR)₂ (historical definition) and Ketal CR¹R²(OR)₂
• Dimethoxymethane (CH₂(OCH₃)₂) in particular, the formal derived from methanol

• A formality, an established procedure or set of specific behaviors
• Pro forma, for no purpose other than satisfying a formality
• Informal activities:
• Informal education, education outside of a standard school setting
• Informal sector, the part of an economy that is not taxed, nor monitored by any form of government
• Informal settlement, or shanty town
• Informal value transfer system, outside the conventional banking system
• Informal social control, enforcing norms without resort to laws

• Informal vote, a spoiled, void, null vote cast in an election
• MV Formality, coaster (formerly Empire Favourite) owned by F T Everard & Sons, scrapped in 1962

• Form (disambiguation)
• Formalism (disambiguation)
• Formal theory (disambiguation)