"Vegetarian" is a valid keyword for a food image containing eggs, cheese, etc., because lacto-ovo vegetarians eat those products. "Vegan" would not be a valid keyword for those images, because vegans do not. The notion of "a true vegetarian" is a personal opinion, i.e., not a taxonomic category that a photographer should use for keyword choices. This highlights the other side of the keyword conundrum, buyers need to use the correct words too. If you want vegetarian food photos that do not include any animal products, you should be searching for "vegan."
Also, this only looks at one use case, and should not be treated as definitive. While one buyer may not search based on the colors in an image, another buyer may have very specific color needs without caring at all what kind of bean is in the soup.
Correct keywords is absolutely essential!
I am both contributor and imagebyer. When searching on a clients behalf the searchwords can be very specific with words like: adhesion, excavator, bitumen etc.
You can find a lot of tape-images here without the keyword adhesion...
One little tip is to use Wikipedia. Very useful, especially for all of us who is not native english spoken. And do not use automatic translation. Also, do not write keywords your not sure of before double checking.
Nikon system. D750 and D7100 are the latest cameras.
Ahaa! Thanks for sharing your perspectives... You know, it's so infrequent that the image buyers weigh in here on their thoughts and needs, That it's like finding buried TREASURE when you do. We contributors do tend to engage in a lot of guessing and assuming in our work. If you look at my keywords, you'll find "organic" and "vegetarian" A LOT, lol, because I didn't know any better, and I do produce a lot of fruit and vegetable imagery, and I figured some recipe compiler/blog producer/whomever, might be out there looking for that stuff by those names.... WOOPS :) Try not to take it too personally - no one wants to trip you up, we are all just trying to help, haa haa! I will stop unnecessarily keywording "organic", because you do make a very logical point! Thanks again and have a great day! USEFUL!
Watch for spelling errors - today I found a great image (by accident) of Potatoe soup. Potatoe will not appear in searches for Potato.
Also be aware of singulars and plurals, soup does not come up when searching for soups. Apple and Apples are two different keywords, might as well be black versus white. Test your keywords before you publish them.