约定俗成 (yuē dìng sú chéng): By common consent / Become a convention — Meaning & Stroke Order

Although there is no written rule for this greeting method, it has long been established by convention and become part of social etiquette.

Are all conventions and established rules not open to question or change?

In this community, garbage sorting has become an established custom.

We did not fully follow those conventional practices; instead, we innovated.

Within the team, this efficient division of labor is an unspoken agreement established by common consent.

Although not explicitly stipulated by law, this tradition has been established by custom and continued for hundreds of years.

Although the process is cumbersome, reform faces significant resistance because it is conventional and widely accepted.