What A Lingua Franca Does And What It Does Not Do

A shared language is a bridge for particular purposes, not a replacement for anybody's first language.

A lingua franca is a practical solution to a specific problem: two people need to transact and do not share a first language. It gets used for commerce, for travel, for official paperwork, for national broadcast, for anything that has to cross regional lines. Because those uses are visible and public, outsiders often overestimate its depth. They hear it in airports and offices and conclude it is what the country speaks. What they are hearing is the layer designed to be heard by strangers, which is precisely the layer least likely to tell you what a household sounds like.

It is also worth separating language from register. Every language has registers: the way you speak to a small child, to an official, to an old friend, to a crowd. A great deal of what outsiders classify as a different language is sometimes a different register, and a great deal of what they classify as the same language is genuinely two languages that happen to be neighbours. Getting this wrong produces confident statements that locals find baffling, because the categories being used do not match the ones being lived.

The useful mental adjustment is to stop asking what language do they speak and start asking what does each language do here. One language may run the market. Another may run the school. Another may run the kitchen and the lullaby. They are not competitors for a single slot. They are a division of labour, and most people carry the whole set without noticing they are doing anything clever.