- Socrates is a man
- all men are mortal,
- then Socrates is mortal
- S is a P
- all P are M,
- then S is M
- Formal verification works in a formal language to attempt to prove formal properties hold for a formal specification of a formal system
- Formal power series extend the notion of a power series by removing the requirement for convergence. Thus they have the same form as a power series, but their more abstract interpretation, not implying a meaningful sum of the series, can be applied more generally.
- Formal grammar - formal system - formal set theory
- Formal occasions such as a formal dinner party or high tea might require one to wear formal attire such as an evening gown or tuxedo.
- In British English, the formal is the same as the event referred to by American English speakers as the prom.
- Informal -- Casual -- Intuitive