patois

2. The common everyday speech of ordinary people, as opposed to a formal or literary language.

The poet chose to write in the patois of his village rather than in standard French.

3. A private or specialized language used by a particular group, such as a profession.

The doctors slipped into their medical patois, leaving the patients confused.

4. A regional form of a language that differs from the standard version.

In the countryside, older residents still speak a local patois that city dwellers barely understand.