Milkshake v Smoothie
I discovered a little while back that there's a very important part of the English language that many very well-educated and intelligent people are confused about: the distinction between a milkshake and a smoothie. I am going to assert that I'm uniquely qualified to be an authority on this topic. You aren't going to question me because I'm writing a whole blog post on the subject and it's fairly difficult to quickly check whether such an assertion is true. You should believe me because of the copious number of both varieties of delicious frozen drink that I've spent time sipping and pondering.
The good news is that these two items are a non-intersecting set. If using their definitions properly, there is no ambiguous item that could be called one or the other. The definitions, although someone nuanced, are also fairly straightforward.
First, let's define what falls into the constellation of smoothie and milkshake. If you are a drink that does not contain ice cream or ice, you are not a smoothie or a milkshake. "Milkshake" does not mean milk, shaken with flavoring. Smoothies and milkshakes contain no soft drinks. A soda with ice cream in it is a float. Drinks that contain crushed ice with some flavoring in them aren't a smoothie or milkshake either. If you don't have ice cream in a drink and you do have ice, you have to meet very strict requirements to qualify as a smoothie.
This last point leads us to our first assertion about smoothies v milkshakes: if you have no ice cream in you, you are most definitely not a milkshake. You might be a smoothie, though. To determine if you are, check the following. Your overall consistency must be smooth and not icy (this qualification is made obvious by the name, of course). You must also be a dull, not a glossy color (although vibrant is completely acceptable). Above all, your flavor must come from fruit and not from some kind of syrup.
A milkshake, on the other hand, can derive its flavor primarily from a syrup. If you have just ice cream, milk and chocolate, vanilla or strawberry syrup and are blended, you are a milkshake.
A drink that has a single fruit in place of the syrup above is also a milkshake. For instance, peaches, milk and ice cream blended together is a peach milkshake. If you used chocolate ice cream in that mixture, you'd be committing all sorts of cosmic crimes by drinking something that tastes bad when each component could be enjoyed on its own, but you would still be drinking a milkshake.
A smoothie can have as many fruits as you would like blended with ice cream or ice. It often will also contain fruit juice. A single fruit juice blended with just ice cream is a freeze, not a smoothie.
Here's the most contentious point in this taxonomy: what is a drink with ice cream, milk and multiple fruits? Here, there are still deterministic definitions, but a sophisticated pallet is required to discern what each should be called. If the drink is made to emphasize and highlight the flavor of the fruit, then it is a smoothie. If it is made to delight with creaminess and the fruit is a subtle supporting flavor, then it's a milkshake.
Finally, a quick note about frankendrinks. Don't ever mix things that would lead to further complications in this categorization. A drink that is otherwise a smoothie with chocolate syrup added is neither a smoothie nor a milkshake. It is an abomination and will likely go on a rampage through your house if you attempt to make it. Horror movies will be made about your creation for years to come. Please, leave such things be and enjoy your milkshake or smoothie.