Formal language is the widely accepted language of a nation. Informal language refers to slang and different dialects people use.

A formal language is a precise and well-defined system of symbols and rules used to represent and manipulate information. It is typically used in areas such as mathematics, computer science, and linguistics. Examples of formal languages include programming languages, mathematical notation, and formal grammars.

One would use formal language in a business letter because it is a formal means of communication. When writing a business letter, one wants the tone to be professional. Formal language can help the writer to achieve this.

Functional grammer is rule governed behaviour . And knowing the language . Formal grammer is formal learning and knowing about the language.

A situation that calls for formal language is when writing a business proposal to a potential client. Using formal language in this context can convey professionalism and establish credibility, increasing the likelihood that the proposal will be taken seriously.