So this is what I get from dictionary.com:


  1. a number of persons or things regarded as forming a group by reason of common attributes, characteristics, qualities, or traits; kind; sort: a class of objects used in daily living.


  1. any collection or assemblage of persons or things; cluster; aggregation: a group of protesters; a remarkable group of paintings.
  2. a number of persons or things ranged or considered together as being related in some way.

The other dictionaries don't seem to be much different. But I always thought that "class" was one of the set of properties of which objects could be differentiated, while "group" is a set of objects having such properties. Classes would be expected to overlap, groups would more likely be distinct. Given a population of objects, the union of all groups within any single class would combine to be the entire population.

I.e. gender is the class, while male or female are groups defined by that class. Age would be a class, while minors and adults would be groups in that class.

That's what I thought was meant, but I can't tease that out of these definitions, so I guess I have for decades a misconception of meaning.

Is that right? Had I had this wrong for all these years? Or am I just not reading these definitions correctly? They seem to be defining "class" and "group" virtually synonymously.


  • 2
    "Class" and "Group" are used as technical terms in some arcane areas of learning, such as computer science. That doesn't mean the definitions you quote here are "wrong".
    – GEdgar
    Feb 1, 2016 at 14:31
  • I do not think this question is well enough formed to be answered. The OED definition takes up almost two full pages, with 11 different meanings, often subdivided. The word class is used differently in different academic disciplines, as well as in sport (eg 'classes of yacht') not to mention the schoolroom class. 'Group' covers nearly three pages. The question needs much clearer context that it has been given so far to be able to set off a useful conversation..
    – Tuffy
    Oct 30, 2018 at 22:04
  • “class” and “group” are also heavily used in mathematics. It is a gross oversimplification, but still basically true, that both refer to sets with particular properties; i.e., they are similar in the sense of the dictionary definitions that you cited, and not sitting at adjacent spots in the food chain, like what you thought. Oct 31, 2018 at 3:48

3 Answers 3


When I was a math student I was taught that a set could be defined in two equivalent ways: by listing all of its members and by stating the rule that determined whether or not an object was in the set. As I understand you, you call the first a "group" and the second a "class". I've never heard that before but "class" does seem to have a more abstract connotation. At the same time they each have meanings that violate your idea. There is "the class of '15" for example and in algebra "group" has a very different meaning than you propose.

A historical note added a month later: I've been reading a book by Lewis Carroll on symbolic logic written in the 19th century. He used "class" in the way we currently use "set" in mathematics and he used "differentia" for the properties that defined whether or not an item was in the set, or class in his terminology.


In sociology a class is a group of people of similar status, commonly sharing comparable levels of power and wealth. A group refers to any number of people who share some social relation. So a class can contain a lot of groups—the middle class has every so-called race, old people, young people, men, women, etc. At the same time, a class is itself a group, to the extent that people within each class share a social relationship. It is not necessary that everyone within a class know another—they need only be bound by some social benefit, social stigma, cultural influence, etc. And, a group may even contain classes--humanity is itself a group.

In short, class is defined economically, while groups are defined by any number of characteristics that may be as large or as small as you like.

These terms apply in other disciplines as well. In taxonomy, a class is a major taxonomic group below the phylum (or division) and above the order. In other words, there is a taxonomic hierarchy consisting of groups, one of which is class, which comprises organisms that share a common attribute. So in this case, organisms within a class are a group--each contains all members of the other--and there is no overlap with any other groups in the hierarchy.

There are also classes and sets and groups in mathematics and music, and probably other disciplines as well, and they each relate to one another in different ways.

You refer also to a "class of objects used in daily living," which is fine, but while this class will contain certain groups, such as kitchen knives, it is just as easy to define kitchen knives as a class that includes such groups as serrated knives, straight-edged knives, paring knives, etc. So class can be as elastic as group.

In short, these are the kinds of terms that, if it's important to you, you need to define what you mean for those you are addressing. It doesn't matter whether your own understanding was right or wrong, because anyone can define them as they want to--unless they work within these disciplines, in which case they are defined for them by precedent, procedure, protocol, etc. etc.


It looks like the terms use each other in their definitions.

There are places, particularly math texts where the two are defined so that one can be used as a sub-category of the other. But the definition there, which is greater or lesser, is arbitrary. They are words used to describe collections of things. For people a group can be a musical band where a class can refer to the "rich" or the "poor".

I don't think there is a particular requirement that puts one above or below the other except in the context of the usage given.

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