That's not the definition of sugar. Not even if you meant sucrose there (which is different from just a mix of glucose and fructose). Wikipedia puts it:
> Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. ... White sugar is a refined form of sucrose.
I know Wikipedia is not perfect but that matches what I've seen in the past. For example, fructose (by itself) is absolutely a sugar and it would be outrageous to claim it's not because it's not sucrose.
You are correct that that is not the scientific definition of sugar, which is generally any 5 or 6 carbon ring molecule.
However when most people talk about sugar they are referring to table sugar, which is a molecule of glucose (a six carbon ring sugar) chemically bonded to a molecule of fructose (a 5-carbon ring sugar) - otherwise known as sucrose. The first thing your body does when it sees sucrose is split them into a molecule of glucose and a molecule of fructose (this happens in your small intestine). Glucose can be metabolized right away, in any cell, however fructose needs a bit more processing in the liver before cells can use it to generate ATP.
> ... when most people talk about sugar they are referring to table sugar ...
What can I say? (shrug) I disagree, that's not my experience from talking to people in person (about diet; obviously it's a different matter if you're talking about cake ingredients). Anecdotal evidence from replies here on HN seems to agree with you though. Who knows what's more common in reality.
That's not the definition of sugar. Not even if you meant sucrose there (which is different from just a mix of glucose and fructose). Wikipedia puts it:
> Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. ... White sugar is a refined form of sucrose.
I know Wikipedia is not perfect but that matches what I've seen in the past. For example, fructose (by itself) is absolutely a sugar and it would be outrageous to claim it's not because it's not sucrose.