Answer:
A formal language is the language that is used when writing or speaking at professional or academic gatherings or purposes.
Some examples of formal language include
Informal language: I'm sorry for coming late
Formal language: I apologise for my lateness
Informal: I want to let you know...
Formal: I wish to inform you that...
In formal language, there is an official tone to it and it is used to address superiors or equals.