Formal
- Acetal
- Ancient Greek
- Colloquialism
- Dimethoxymethane
- Dynamic and formal equivalence
- Form (disambiguation)
- Formal (university)
- Formal calculation
- Formal cause
- Formal concentration
- Formal derivative
- Formal fallacy
- Formal grammar
- Formal language
- Formal logic
- Formal methods
- Formal power series
- Formal proof
- Formal specification
- Formal system
- Formal theory (disambiguation)
- Formal verification
- Formal wear
- Formalism (disambiguation)
- Informal attire
- Informal education
- Informal fallacy
- Informal logic
- Informal mathematics
- Informal sector
- Informal settlement
- Informal social control
- Informal value transfer system
- Informal vote
- Ketal
- MV Formality
- Naive set theory
- Pro forma
- School formal
- Semi-formal attire
- T–V distinction