What Is a Campaign?

Before we answer the question, let's first consider the dictionary definitions beginning with Merriam-Webster's Collegiate Dictionary Eleventh Edition:

campaign

1 : a connected series of military operations forming a distinct phase of a war

2 : a connected series of operations designed to bring about a particular result <election ~>

The Oxford Illustrated Dictionary is in agreement:

campaign

1. Series of military operations in a definite theatre or with one objective or constituting the whole or a distinct part of the war.

2. Organized course of action, esp. in politics, as before an election.

Before we can connect the "campaign" as it is understood in role-playing games with its more formal definition, we must first look at how it entered the hobby via war games. Dungeons & Dragons, as is well known, emerged from the war game hobby in general and from the medieval miniatures war game Chainmail specifically.

The Advanced Dungeons & Dragons Dungeon Masters Guide gives us this definition:

campaign

General term referring to one DM's adventures as a whole rather than individually. An ongoing series of games based upon a created milieu.

The D&D Basic Set (1980) defines it thusly:

campaign

A series of adventures taking place on the same fantasy world.

It ought to be clear that by any definition, a campaign is a series of activities comprising a greater whole. A single adventure does not a campaign make. Individual adventures can be likened to the chapters in a book — the campaign is the book itself.

I confess I've never been partial to "campaign" as a term to describe a series of adventures. The word is overtly military and suggests carefully planned strategy to achieve a specific objective, which I feel rarely describes the activities of player characters. I'd prefer to call it a "series of adventures" because that's what it is. Sometimes we, as human beings, are prone to classify and apply terminology to things that don't necessarily require either classification or unique (or not-so-unique) terms to be understood. I prefer clarity.

Although I'll admit "campaign" is slightly more succinct.