Punjabi is the name of a language, so it is spelled with a capital P wherever it sits in the sentence. As a language name it is uncountable: you say speak Punjabi, learn Punjabi, in Punjabi, and you do not put a or an in front of it and do not add -s. Millions of people use it at home, at work and in songs and films, and many of them live far from the Punjab itself, because families take the language with them when they move. The word is also used for a person from the Punjab, and as an adjective; those are separate entries here. An older spelling, Panjabi, still appears in some books.

Used of people, Punjabi is countable: a Punjabi, two Punjabis. It covers someone born in the region and also someone whose parents or grandparents came from there and who now lives somewhere else. The source also records it for a person who speaks the Punjabi language, so the two ideas sit close together and are often true of the same person, but they are not identical: a person can speak the language without being from the region. The capital P stays. The form Panjabi means the same thing, and older books also show Panjabee, Punjabee, Punjaubee and Panjaubee.