You're right that the FDA definition of mayonnaise requires egg. This comes from depression-era laws where people were passing fraudulent products off as the real thing. I think those laws still matter, but kind of miss the point here.

As a different way to look at it, imagine a sort of food Turing Test. If it looks like the thing, it behaves like the thing in every meaningful way, and its taste is indistinguishable from the thing, is it not the thing? Maybe, maybe not, but I think it's an interesting question worth exploring.

Wikipedia says "Mayonnaise is a thick, creamy dressing often used as a condiment. It is a stable emulsion of oil, egg yolk, and either vinegar or lemon juice, with many options for embellishment with other herbs and spices." Random House says "a thick dressing of egg yolks, vinegar or lemon juice, oil, and seasonings, used for salads, sandwiches, vegetable dishes, etc." Oxford Learner's Dictionary says "a thick cold white sauce made from eggs, oil and vinegar, used to add flavour to sandwiches, salads, etc.". Merriam-Webster says "a dressing made chiefly of egg yolks, vegetable oils, and vinegar or lemon juice". Oxford dictionary says "A thick creamy dressing consisting of egg yolks beaten with oil and vinegar and seasoned."

Who's definition of mayonnaise doesn't involve eggs? How would you even define it except by mentioning eggs?

I'm not arguing that you're wrong about what mayonnaise is, I'm adding a wrinkle to the concept of defining a food product.

I don't have much of a dog in this fight, I personally care that it "does what it says on the tin" rather than fits a dictionary or other definition. That said I understand the counterpoint, I just think it's not quite as black-or-white.

That's sort of the crux of the matter, when we say "mayo" we mean the thing with egg in it, not anything that resembles the thing with egg in it.

If you'd like to say, "let's stop defining mayo as the thing with egg in it," then maybe that's a discussion worth having, but it's a different issue than just, "can't we call this other thing that isn't mayo, mayo?"

There are a ton of laws that govern how you label food, many of them explicitly passed to stop the exact thing you're suggesting. And these laws both stem from and reinforce a strong cultural/linguistic assumption that if you say "noun" you mean a noun, and if you say "adjective noun" you mean a noun that differs from normal examples of that noun by some specific characteristics.

Hence, we have "vegan cheese", "turkey bacon", "butter with canola oil", "non-dairy creamer", "vege burgers", "sugar-free cola", and a host of other examples. When a company (now owned by Unilever) went to launch a low cost spread they believed tasted just like butter onto the market, they didn't call it "Super Butter", they called it "I Can't Believe It's Not Butter!".

Or if you prefer, flip it around: Hampton Creek has gone to some lengths to brand their vegan mayo in such a way that it looks as much like normal, non-vegan mayo as possible; so much so that they've ended up in disputes with the FDA and been forced to modify their packaging. It would have been cheaper and easier for them to have just said "vegan mayo" and called it a day, but they didn't. Why? Well, probably in part because they believe that some customers would choose to not buy "vegan mayo" if given a choice. Packaging that exists merely to deceive consumers is problematic, even if the consumer's in question are trying to make misguided or short sighted decisions.

(This is highly analogous to the ongoing debate about GMO labelling. Producers of GMO ingredients say that food containing them is indistinguishable from food that does not, so no label is or should be required. But many customers, rightly or wrongly, would rather avoid GMO foods. It's not clear to me what the right decision there is, but I don't think it's correct to pretend there can't be a valid debate.)

I agree that mayonnaise should be defined by the ingredients, but I bet a majority of people who eat mayonnaise (or Miracle Whip thinking it is mayonnaise) don't know it is made from egg yolks. For those people the definition would be a white creamy spread that goes on bologna sandwiches. Their definition is external (taste, look), not based on the ingredients.

- can be carried in your pocket - are wireless - have high-resolution screens - are supercomputers, by standards of 1984 - can send video just as easily as voice

Some words describe function, not a list of ingredients.

Some words change meaning over time.

Sometimes the thing described changes drastically, like bananas http://www.businessinsider.com/banana-fruit-changes-history-...

We didn't create a new word to describe iPhone.

Just Mayo has more in common, functionally speaking, with egg-based mayonnaise than iPhone has with rotary phone or Tesla with Ford's Model T.

"Just Mayo has more in common, functionally speaking, with egg-based mayonnaise"

Mustard, catsup, ranch dressing, and many other condiments also have a lot in common with mayonnaise functionally. That doesn't make them mayonnaise.

According to this viewpoint, it would be okay to label Kool-Aid and orange Fanta as "fruit juice". No.

I've never seen an appellation applied to mayonnaise, have you?

It comes from companies like HC still trying to lie on the labels.

This is why you can buy margerine and other butter substitutes under names other than "butter".

This is why you can receive entertaining fantasy fiction on Fox but not have it called New... never mind.

I personally would have thought that an eggless mayo thing that tastes good would have made the eggless thing a selling point but I guess not. Presumably they're trying to avoid the reflexive it can't be good if it doesn't have eggs in it.

(Personally I use Hellman's in any case.)

I agree with your parent. "Just Mayo" sounds like.. just mayonnaise. It should be called a made-up term like "Vayo: the vegan mayonnaise" or similar.

"Just Mayonnaise" implies to me, "This is just mayonnaise". The egg-free should be more prominent and "just" shouldn't be in the title. "Just $NOUN" usually means "This and only this without anything added (or, as I infer, removed or replaced).

Which is fine; “vegan mayonnaise-flavored spread” would be accurate and in line with how other food products which are distinct from but designed to emulate a pre-existing food product category have been labelled for many years.

“Vegan mayonnaise” is no more coherent a label than “vegan pork”.

Incidentally, the word "just" in their product names refers to the adjective related to "justice," not the term meaning "only." There is a note on the product explaining this.

(Edited to remove a comparison because I forgot people hate comparisons.)

The definition of egg does not include the color of its shell.