The subject or theme under discussion.

• A general area of interest or study.

A thread or conversation on a forum or platform.

• The initial post and its replies as one unit.

In messaging systems, a named channel for publish and subscribe.

• Delivers messages to multiple subscribers.

In music, a conventional style marker suggesting a genre.

• Evokes a familiar musical topic like march or pastoral.

In rhetoric, a commonplace or line of argument.

• A general category from which arguments are drawn.

Archaic: an external medicinal application, such as a plaster or blister.

• Applied to the skin rather than taken internally.