Quick note: What does the word "vegetarian" mean?

Short summary: If a food is "vegetarian" that means that this food does not include any body parts of any type of animal. A vegetarian person therefore is someone who does not eat any foods that are body parts of animals - usually this means "flesh foods", i.e. the muscle tissue of animals such as fish, cattle ("beef"), pigs ("pork"), goats, "sheep", chickens, turkeys, ducks, geese ("poultry"), rabbits, squids, etc. The term "meat" is not precise as many people tend to include or exclude for example fishes ("fish") in its definition.

There is some confusion about what the definition of "vegetarian" is. This confusion is highly prevalent amongthe general public, but also among self-described "vegetarians", and even among nutritional scientists. So, if you, too, are confused, don't be sad! You are in good - but confused - company.

The definition of a "vegetarian" person:
A vegetarian is a person who does not eat any "flesh foods", i.e. foods made from the flesh of animals - this includes all types of meats and sausages, all types of fishes and all types of other animals (including insects, turtles, snakes, shrimps, mussels, and all other animals). 
But to be precise, it is not just about "flesh". Blood and bones are not flesh (muscle tissue). One can argue that skin is not flesh either - "flesh", too has various definitions - but clearly, eating the skin or bones or consuming the blood of any animal cannot be considered vegetarian either.

Rule of thumb for vegetarian persons: If it is a body part of an animal, and you eat it, you are not a vegetarian (no judgment included - this is about a definition, not about moral judgment).

Rule of thumb for vegetarian foods: If it is or contains a body part of an animal it is not a vegetarian food.

Rule of thumb for people with a short attention span: Vegetarians do not eat animals.

What about animal secretions? Are animal secretions "body parts", too?
For the sake of simplicity, let's argue that animal secretions are not body parts.
Widely eaten animal secretions are milk (which comes from mammals, i.e. animals that lactate after pregnancy), bird's eggs (especially from chickens), and honey. These foods are vegetarian, but not all vegetarians eat them. Vegans, for example, do not eat any foods that come from animals - whether body parts or secretions.  

But who has the right to define what "vegetarian" means?
Technically, everybody can decide for themselves, but if everybody decides the meaning of words themselves that will make communication difficult.

Generally speaking, I would suggest vegetarians should decide what vegetarianism is, rather than non-vegetarians deciding. The Vegetarian Society in the United Kingdom supplies a useful definition:

Definition of a vegetarian (Vegetarian Society UK): "Vegetarians don't eat fish, meat or chicken [...]".

You can see that a large print part of the definition is more pragmatic, whereas the small print sections goes into details that many real-life vegetarians do not adhere to (such as avoiding gelatine, animal-based rennet, etc.).

The UK Vegetarian Society was founded in 1847, several years after what very likely was the first use of the word "vegetarian" in history. It seems quite likely that the first usage of the word "vegetarian" occurred at Alcott House, the seat of a small Christian socialist, "mystical", vegetarian community in Richmond, Surrey (today Greater London), named "The Concordium". The members of this small group seem to have followed a vegan diet, and the original meaing of the word "vegetarian" might have been "vegan" (i.e. excluding all animal products) - but this is not how the word "vegetarian" is understood today. 

The European Vegetarian Union in May 2018 reported the definition of "vegetarian" by Food Drink Europe (FDE) - a definition meant for use in future legislation.

"Proposed definition (translation by EVU) The following proposed definition has been adopted by the German consumer protection minister conference (see above) and approved by FDE. The EVU sees the requirements depicted above as fully implemented in this wording and suggests to use it for further discussions. 
(1) Food suitable for vegans 
Foods that are not products of animal origin and in which, at no stage of production and processing, use has been made of or the food has been supplemented with 
- ingredients (including additives, carriers, flavourings and enzymes), or 
- processing aids, or 
- substances which are not food additives but are used in the same way and with the same purpose as processing aids, that are of animal origin. 

(2) Food suitable for vegetarians 
Foods which meet the requirements of paragraph 1 with the difference that in their production and processing 
1. Milk and dairy products, 
2. Colostrum, 
3. Eggs (No. 5 of Annex I to Regulation (EC) No. 853/2004), 
4. Honey (Annex I to Directive 2001/110/EC), 
5. Beeswax, 
6. Propolis, or 
7. Wool grease including lanolin derived from the wool of living sheep or their components or derivatives may be added or used." (European Vegetarian Union, May 2018, checked 23 March 2019

Definition of "vegetarian" by the Oxford Dictionary of English (United Kingdom):
Vegetarian: "A person who does not eat meat or fish, and sometimes other animal products, especially for moral, religious, or health reasons."
Mid 19th century: formed irregularly from vegetable [as in "of plant origin"] + -arian." [This is correct. The word "vegetarian" does not originally come from the Latin "vegetus" - this was an early, but later idea, that was then widely repeated.] (English Oxford Living Dictionaries website, checked 23 March 2019)

Definition of "vegetarian" the Merriam-Webster (United States of America) dictionary:
Vegetarian (noun): 
(1) "a person who does not eat meat: someone whose diet consists wholly of vegetables, fruits, grains, nuts, and sometimes eggs or dairy products" [This is not precise, as mushrooms, salt, etc. are also consumed by vegetarians.]
(2) "herbivore"
Vegetarian (adjective):
(1) "of, relating to, or suitable for vegetarians"
(2) "not containing meat: consisting wholly of vegetables, fruits, grains, nuts, and sometimes eggs or dairy products" (Merriam-Webster dictionary website, checked 23 March 2019)

The German dictionary "Duden" (the quasi-official dictionary of the German language) gets it a little wrong. The Duden states:
Vegetarian (noun):
"jemand, der sich [vorwiegend] von pflanzlicher Kost ernährt" This means: "someone who follows a diet [predominantly] of plant origin".
Someone who follows such a diet follows a plant-based diet, which might include meat. So this is not at all a correct definition of "vegetarian". (Duden website, checked 23 March 2019)

The Spanish dictionary by the "RAE" (i.e. the officially official dictionary of the Spanish language) defines "vegetarianism" as:
Vegetarianism (noun):
"Del ingl. vegetarianism.
1. m. Régimen alimenticio basado principalmente en el consumo de productos vegetales, pero que admite el uso de productos del animal vivo, como los huevos, la leche, etc.
2. m. Doctrina y práctica de los vegetarianos." 
This means: "From the English 'vegetarianism'".
(1) A diet based mostly on the consumption of plant foods, but that admits the use of products from living animals, such as eggs, milk, etc."
(2) "The doctrine and practice of vegetarians" (RAE website, checked 23 March 2019
That means, that the RAE defines "vegetarianism" as "ovo-lacto-vegetarianism".

How do nutritional scientists who research vegetarian dietary patterns define the word "vegetarian"?
Two of the biggest studies that research the health effects of vegetarian/vegan diets are the Adventist Health Study 2 (AHS-2; conducted by researchers from Loma Linda University, California, USA) and the EPIC-Oxford study (conducted by researchers from Oxford University, UK).

In their publications the EPIC-Oxford researchers generally use the "correct" (precise) definition of "vegetarian" (see table below). In contrast, the AHS-2 researchers tend to use somewhat incorrect definitions - but for the purpose of studying the effects of vegetarian diets these definition are quite useful: The AHS-2 researchers, for the purposes of their study, define "mostly vegetarian" as "vegetarian" and "mostly vegan" as "vegan" (see table below - please click on the table or open it in a new tab to see the full size image).    

For those who are really interested here are some quotes from recent EPIC-Oxford as well as AHS-2 publications, that show how vegetarianism is defined by these researchers:

EPIC-Oxford:Vegetarians, who do not eat any meat, poultry or fish, constitute a significant minority of the world’s population. Lacto-ovo-vegetarians consume dairy products and/or eggs, whereas vegans do not eat any foods derived wholly or partly from animals” (Appleby and Key 2016) [This is a correct definition of “vegetarian”.]

EPIC-Oxford: “[…] vegetarians (who do not eat meat or fish but do eat dairy products and/or eggs)” (Schmidt et al. 2016) [This is a definition of “ovo-lacto-vegetarian”.]

EPIC-Oxford: “[…] vegetarian diet (containing no meat or fish)
Participants were also asked whether they ate meat, fish, eggs or dairy products, and, where appropriate, the ages at which they stopped eating these foods, and were categorised as vegetarian if they did not eat meat or fish at the time of questionnaire response.” (McConnell et al. 2017) [This is a correct definition of “vegetarian”.]

EPIC-Oxford: “[…] vegetarians (ate no meat or fish, including vegans[)]” (Papier et al. 2019) [This is a correct definition of “vegetarian”.]

AHS-2: “[…] individuals classified as vegetarian (vegan, lacto-ovo-vegetarian, pesco-vegetarian, semi-vegetarian) [This is an INCORRECT definition of “vegetarian”, that is NOT USEFUL either] and non-vegetarians […] 4 vegetarian dietary groups [referring to the four groups in brackets in this sentence; pesco-vegetarians or semi-vegetarians are NOT vegetarians, obviously.]
Vegetarian diet patterns are characterized not simply by the absence of meat and/or dairy products [This is an INCORRECT definition of “vegetarian”. Dairy-free diets do NOT have to be vegetarian!] but also by increased consumption of plant foods.
Roughly 52% of participants follow a vegetarian diet (including vegans and lacto-ovo-vegetarians) [This is a CORRECT definition of “vegetarian”, contradicting the incorrect definition above] or partially vegetarian [CORRECT] diet (including pesco-vegetarians and semi-vegetarians, with the latter consuming meat more often than once a month but less than once per week), and the others are non-vegetarian.
Participants were classified a priori into vegetarian diet groups based on their responses to the FFQ as follows: vegans never or rarely (less than once per month) consumed eggs, dairy, fish, and other meats; lactoovo-vegetarians consumed eggs and dairy more than once per month but fish and other meats less than once per month [These definitions are USEFULL in terms of the study, but NOT CORRECT and should not be used outside the context of this or similar studies]; pesco-vegetarians consumed fish at least once per month but all other meats less than once a month; semi-vegetarians ate non-fish meats at least once per month and any meat including fish less than once per week; nonvegetarians consumed non-fish meats at least once a month and any meat (including fish) more than once per week” (Miles et al. 2019)  


  • Appleby, Paul N.; Key, Timothy J. (2016): The long-term health of vegetarians and vegans. In The Proceedings of the Nutrition Society 75 (3), pp. 287–293. DOI: 10.1017/S0029665115004334.
  • McConnell, T. J.; Appleby, P. N.; Key, T. J. (2017): Vegetarian diet as a risk factor for symptomatic gallstone disease. In European journal of clinical nutrition 71 (6), pp. 731–735. DOI: 10.1038/ejcn.2016.252.
  • Miles, Fayth L.; Lloren, Jan Irene C.; Haddad, Ella; Jaceldo-Siegl, Karen; Knutsen, Synnove; Sabate, Joan; Fraser, Gary E. (2019): Plasma, Urine, and Adipose Tissue Biomarkers of Dietary Intake Differ Between Vegetarian and Non-Vegetarian Diet Groups in the Adventist Health Study-2. In The Journal of nutrition. DOI: 10.1093/jn/nxy292.
  • Papier, Keren; Appleby, Paul N.; Fensom, Georgina K.; Knuppel, Anika; Perez-Cornago, Aurora; Schmidt, Julie A. et al. (2019): Vegetarian diets and risk of hospitalisation or death with diabetes in British adults: results from the EPIC-Oxford study. In Nutrition & diabetes 9 (1), p. 7. DOI: 10.1038/s41387-019-0074-0.
  • Schmidt, J. A.; Rinaldi, S.; Scalbert, A.; Ferrari, P.; Achaintre, D.; Gunter, M. J. et al. (2016): Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. In European journal of clinical nutrition 70 (3), pp. 306–312. DOI: 10.1038/ejcn.2015.144.