It’s a bit hard to believe that in 2012 anyone is still unclear about what “peak oil” means, but enough confusion about it has surfaced in the past week that I feel compelled to, once again, try to set the record straight.

“Peak oil” refers to the maximum rate of production of regular crude oil. Period. It’s a number.

It is not a theory.

It does not mean “running out of oil.”

It is not the moral equivalent of Malthusianism.

It is not a political movement, or a religion.

It’s not a dessert topping. It is not a floor wax.

It is not about oil reserves (oil that has been proved to exist and to be producible at a profit), or resources (oil that may exist in the ground, irrespective of its potential to be produced profitably). Those quantities do play a role in estimating the peak, but do not determine it in any way.

“Peak oil” is not the same as “the end of cheap oil,” although the latter is also true. Price is not a proxy for production.

“Unconventional” liquids such as biofuels, natural gas liquids, synthetic oil made from bitumen in tar sands or from kerogen in shales, and liquids made from coal or natural gas are not regular crude oil, nor are they equivalent to crude on several important counts. When you’re talking about unconventional liquids, you are not talking about oil, and lumping them in with oil does not increase the volume of oil. That’s why it’s called “peak oil” and not “peak liquid fuels.”

This is why I insist on the term “tar sands.” They contain not oil, but bitumen, a low-grade hydrocarbon which is a tar-like solid at room temperature, and must be upgraded with substantial inputs of energy to turn it into a synthetic oil. Calling them “oil sands” is nothing but a PR stunt.

Likewise, if you’re not talking about data on oil production rates, or the general topic of reaching the peak rate, then you’re not talking about peak oil.

I hope that’s clear, and I hope to never have to say it again.

Since it may seem pedantic to be so fussy about the definition, I will explain why it matters.