There are often debates here about what is a zoo. I came across the definition of the word "zoo" as adopted by the World Association of Zoos and Aquariums (WAZA) and thought I would share it here: "Permanently sited facility, primarily open to and administered for the visiting public, with living wildlife and other species." Exactly the same definition is given for "aquarium".
I've posted this before and will again. Here is my personal definition of a zoo: The facility must be open to the public for at least three months of the year. The primary purpose of the facility is to exhibit captive animals OR to teach about nature via captive animals. The facility must display at least 3 species, at least two of which must be exotic (non-domestic) species. You must be able to visit the facility without a guided tour. The primary purpose must not be too sell animals. The facility may still count if it does sell animals, as long as it is not the primary purpose. The facility must be permanent and be at a fixed location.
I predominately agree with this definition but I think it should also be added that the facility must have a primary focus on non-aquatic animals to differentiate "zoo" from "aquarium."
Why 3 months of the year? There are some zoos which are only open weekends and public holidays. Why specifically a minimum of 3 species? Do single species facilities exist? There are facilities where you can only visit via guided tours, often a bus or monorail system. Not sure you have this as a limiting factor.
I'm not sure this can be right. Let's say that Chester Zoo decided for whatever reason to only open in July and August every year. Would it not be a zoo?
I think the phrase "primarily open to and administered for the visiting public" covers your second and fifth requirement and to an extent your first requirement in that: A hotel with an exotic animal collection is being administered for hotel guests. A doctor's surgery with a tropical fish tank is being administered for patients. A pet shop selling exotic animals is being administered for pet purchasers. A facility which is not open when the visiting public want to visit is not being administered for the public, but if the public only want to visit say during the summer school holiday, then that is enough. I don't agree with your guided tour requirement so long as sufficient guided tours are available to meet normal demand, ie again is the facility being administered for the public or an elite group. I'm not sure if the number of species matter.
I think 'aquarium' is primarily a type of exhibit, not necessarily a different type of facility. Many zoos contain aquariums, indeed the first public aquarium was and still is an exhibit area in a zoo. Likewise many self described aquariums include substantial collections of terrestrial animals, and some, such as Dallas World Aquarium, are primarily terrestrial facilities.
I basically agree with this - with the corollary that the facility should have a main/major focus on wildlife instead of other attractions. There are city parks with fowl aviaries, natural history museums with a couple of vivaria, and theme parks with some farmyard animals, but I'm not sure I would consider these "zoos". I also consider aquaria (and bird parks) to be a subcategory of zoos rather than a different category. All aquaria are zoos, but not all zoos are aquaria.
Generally I would agree with statements above. It greatly shows for me what a zoo practically is. I would like to add something small but for me really important note - a zoo, especially a zoo of XXI century, should be a place which creates significance-meaning, constructs and images of animal species and other zoology-related themes (e.g. ideas connected with zoology, conservation). I think that being a "park with a lot of animals" and even speaking "we save species" is way too small today (however very important, at least that second one). I mean a situation: almost everyone knows what a lion is - or tiger - and has in their had a meaning of lion/tiger. What about showing and creating meaning of little charming tree-climbing master (like margay)? Doing something like Madagascar done with lemurs - now people know and love lemurs. So for me a zoo is a place which combine a conservation breeding with building meanings of [less-known] species. Because I see it in the middle - on the one side is science and on the other a park for pleasantly spending time with nature. For me this situation has a lot of possibilities to save nature. Maybe, I feel it more idealistically and yes, I know I'm not master of English... (however I tried!)
It's interesting the animals aren't mentioned in the definition. According to the Cambridge English dictionary wildlife can also refer to plants (WILDLIFE | meaning in the Cambridge English Dictionary) so a botanical garden is a zoo under the WAZA definition.