What might you call one specific fact

A fact? Because if its one fact or 7, they would still be facts

If, for instance, you say, "Using their legions, the Romans conquered many lands," you leave a great deal in question. How did their legions achieve such dominance? Whom did they defeat, and when? Were legions the sole agents responsible for Rome's triumphs, or did issues of leadership and management in the wake of conquest play a role in Rome's dominion, too?