We could be here all night. The topic under discussion is dimly lit and shrouded in smoke. Anyone can try it — most of us have. But even with a lifetime of familiarity, its fundamentals are hard to pin down. What, exactly, is pool?

For instance, is it a sport? For decades the question has been pondered by — in ascending order of importance — lawyers, philosophers, sports pundits, the International Olympic Committee and barroom sports fans, without consensus. Sure, it’s played on a table, but so is table tennis — and that’s an Olympic sport. Yes, it’s an indoor activity, but so is basketball. And yes, you can smoke and drink during a competitive match.

What is it actually called? Strictly speaking, it is not “pool” at all, but a variant of pocket billiards. Pool refers to the collective betting that became attached to the outcome of some matches in public billiard parlors in the 19th century. In time, the name of this sideshow was adopted as the popular moniker for the main event.

The formal title for what most of us now know as pool is eight-ball billiards. Popular variations include snooker ( www.worldsnooker.com ), which is especially well-known inBritain and the countries of the former British Empire, and the French traditional pastime of carambole billiards ( www.umb.org ), which has been going strong since the 1700s.

What are the rules of pool? Now it gets complicated. They often depend on what country you’re in, on the region of the country, on the pool hall, on the dimensions of the table and whom you’re playing.

In a bar in Belize, I once had to adhere to a set of rules designed to accommodate the fact that the cues were half the usual length (thanks, apparently, to a mass brawl some years before). And in Bolivia, protocols had been devised to cope with the regular circumstance of the resident cat jumping up and flicking the balls off the table.

Even at the professional level, there is no single rule book, and several rival governing bodies continue to vie for supreme jurisdiction over the world’s pool tables. The Billiard Congress of America ( www.bca-pool.com ) has proposed the “World Standardized Rules,” though as these do not encompass half-length cues, rogue cats and innumerable other global quirks, their influence remains limited.

As long as the participants have agreed the terms under which they’re playing in advance; it really doesn’t matter which set of rules they observe. The underlying principle is constant. When you strip it down to the basics, pool is a form of rocket science. Every shot is a complex marriage of geometry and velocity.

Taking aim and applying the perfect measure of force requires hand eye coordination and muscle memory, aptitudes that surely place pool within the pantheon of world sports. In the past 20 years, there has been a concerted effort to gain Olympic status for billiard sports, and perhaps they will feature in the London Games in 2012. Though it is unlikely that the sporting purists will be silenced, for they will probably always regard pool as no more than a common bar game.

And yet, it is precisely those unpretentious origins that make pool, in its authentic setting within the smoky barrooms and billiard halls of the world, one of the most egalitarian of sports. You don’t need to be born with an athletic physique, or to observe a strenuous training regime, or even to purchase special equipment. Put a coin in the slot, rack the balls up and begin. We could be here all night.