Formal, formality, informal or informality imply the complying with, or not complying with, some

set Set, The Set, SET or SETS may refer to: Science, technology, and mathematics Mathematics *Set (mathematics), a collection of elements *Category of sets, the category whose objects and morphisms are sets and total functions, respectively Electro ...

of requirements (

form Form is the shape, visual appearance, or configuration of an object. In a wider sense, the form is the way something happens. Form also refers to: *Form (document), a document (printed or electronic) with spaces in which to write or enter data ...

s, in

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

). They may refer to:

Dress code and events

Formal wear Formal wear or full dress is the Western dress code category applicable for the most formal occasions, such as weddings, christenings, confirmations, funerals, Easter and Christmas traditions, in addition to certain state dinners, audien ...

, attire for formal events *

Semi-formal attire Semi-formal wear or half dress is a grouping of dress codes indicating the sort of clothes worn to events with a level of formality between informal wear and formal wear. In the modern era, the typical interpretation for men is black tie for ev ...

, attire for semi-formal events *

Informal attire Informal wear or undress, also called business wear, corporate/office wear, tenue de ville or dress clothes, is a Western dress code for clothing defined by a business suit for men, and cocktail dress or pant suit for women. On the scale of fo ...

, more controlled attire than casual but less than formal *

Formal (university) Formal hall or formal meal is a meal held at some of the oldest universities in the United Kingdom and the Republic of Ireland (as well as some other Commonwealth countries) at which students usually dress in formal attire and often gowns to ...

, official university dinner, ball or other event *

School formal A promenade dance, commonly called a prom, is a dance party for high school students. It may be offered in semi-formal black tie or informal suit for boys, and evening gowns for girls. This event is typically held near the end of the school y ...

, official school dinner, ball or other event

Logic and mathematics

Formal logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premis ...

, or mathematical 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

Computer science

*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

Linguistics

*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 *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

Chemistry

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

Social regulation

* 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

Other

* Informal vote, a spoiled, void, null vote cast in an election * MV Formality, MV ''Formality'', coaster (formerly ''Empire Favourite'') owned by F T Everard & Sons, scrapped in 1962