When, in a group of propositions, one proposition is claimed to follow from the others, that group is called

A group of propositions in which one is claimed to follow from the others is an argument.

Within it some propositions act as premises and one acts as the conclusion.

The defining feature is the claim of support or inferential connection between them.

Mere validity or invalidity is a further judgment, not the basic definition.

Any such inference-bearing set of propositions is by definition an argument.