Yes, it’s confusing. And yes, one’s first inclination is to make a joke — or several (and there is a wine called K Syrah).

But given the increasing popularity of syrah and shiraz, it’s probably a good idea to remain straight-faced — at least long enough to explain the difference between the two, as well as to figure out where their much-less-known cousin, petite sirah, fits in.

First, syrah and shiraz are the same grape. Wines from the Rhone region of France, California, and the Pacific Northwest are called syrah, while those from Australia are called shiraz. Petite sirah is genetically similar to syrah, and almost certainly evolved from it, but it’s not as intense or as bright.

The real difference is in style. Generally, shiraz is much less subtle than syrah, and the reason is mostly climate. Australia has a longer growing season than the Rhone, California and the Pacific Northwest, so the grapes become more ripe, which means more intense flavor and more sugar. And more sugar means more alcohol during fermentation, often as much as 1 to 2 percentage points more.

The following are a good example of what each style includes:

• Columbia Crest Two Vines Shiraz 2003 ($10). Though it’s called shiraz, it’s made more in the syrah style — less jammy flavors, and blended with grenache and viognier, a white grape, to tone down the syrah.

• Nine Stones Shiraz McLaren Vale 2003 ($15). It doesn’t get much more Aussie than this — chewy, almost ashy wine with an inky color, made in the style that the wine magazines drool over.

• Domaine Gramenon Cotes du Rhone Les Laurentides 2001 ($16). Classic southern Rhone wine. This is about two-thirds grenache, but the one-third that is syrah gives it its backbone and an intriguing spiciness.

• Michael-David 6th Sense Syrah 2003 ($17). This is a California wine from Lodi made more in the Australian style — higher alcohol, more jammy flavors, and blended with cabernet and petite sirah instead of Rhone varietals.