Signage, forms and broadcasts in a city may all be in one language while a good deal of daily conversation happens in another. The gap is common and it has a consistent structure.
Official and domestic languages diverge
National administration usually standardises on one language for practical reasons. Courts, schools and bureaucracy need a single medium, and that choice becomes the visible face of a place.
Households do not standardise. Families continue in whatever language the previous generation used, and that continues unaffected by what appears on a road sign.
The result is a city that reads as monolingual and sounds otherwise. Visitors reading the signs get an accurate picture of the state and an incomplete one of the population.
Markets are where the second language surfaces
Commerce follows convenience rather than policy. In markets, workshops and small shops, traders use whichever language moves goods fastest with the customers in front of them.
That makes markets the most linguistically honest part of a city. A visitor listening rather than reading will hear the actual distribution within a few minutes.
Transport hubs behave similarly. Drivers, porters and vendors work across communities and accumulate practical fluency in several codes.
Migration keeps supply renewed
Cities draw people from surrounding regions, and each wave arrives with a regional language. Neighbourhoods form around origin, and the language persists inside them.
Second generations typically become bilingual, using the national language outside and the home language within. The domestic language survives without ever entering public life.
Where migration slows, the pattern fades within a couple of generations. Where it continues, the second language is continually topped up by new arrivals.
Older residents hold the deepest version
The most complete form of a local language usually survives among older speakers who learned it before schooling standardised. Vocabulary for trades, agriculture and weather often exists only there.
Younger speakers frequently use a mixed register, switching mid-sentence. Linguists treat that mixing as a stable form in its own right rather than as decay.
Documentation projects tend to focus on the older register for this reason. Once that generation goes, the specialised vocabulary is rarely recoverable.
What this means for a visitor
Learning a few phrases in the local rather than the national language changes reception noticeably. It signals that the visitor has noticed something most do not.
It also explains why translation apps struggle in some places. They are trained on the standardised written language and encounter something the corpus never captured.
Asking which language a person prefers is the safer approach. In multilingual cities the question is normal, and the answer often reveals more about a neighbourhood than a guidebook does.