The mass of an object is defined as the "amount of "matter" in an object, whereas weight is the force exerted on an object by gravity".

However, I often see in scientific literature the adjective "large" associated to mass/weight, such as "this animal is larger than another", or "small animals". Is this correct or would "heavier" be the correct adjective to use?

Mind you that volume is never discussed in these texts, they always discuss mass/weight in Kg. This trend can be observed in top scientific journals such as Science or Nature, so what would be considered the most authoritative scientific references.

Maybe this applies also to other contexts.

EDIT: I am not interesting in discussing the difference between mass and weight. I am wondering why authors are using "large animal" when there's no volume or size involved, instead they mean "heavy animal".

  • 2
    An ostrich, for example, is a bird. Which presumably means it has lighter bones than, say, mammals. Plus much of the "size" of an ostrich is accounted for by stereotypically lightweight feathers. So I'm sure there must be mammals that are heavier, but not so large as ostriches. Mass, volume, size, and weight are conceptually different. Nov 6, 2020 at 15:53
  • I guess that you mean heavy, or massive, as mass X gravity, or just plain old mass, respectively. In which case, simplistically speaking, it's the gravitational field intermediates between the two. This is the distinction between gravity, and gravitation. So, without further delving into what, exactly, is the connection from neither the mass nor the gravity side of things per se, I would, somewhat incorrectly, say, gravitational objects. Nov 6, 2020 at 16:14
  • If all you wanted to know was Which of heavy mammals, large mammals is more common?, you could have done that same search as me on Google NGrams. I'm afraid I think this question is just Too Basic for ELU. Nov 6, 2020 at 18:03
  • 2
    Large and small are relative terms. Mercury is a small planet, but its mass is much more than that of the largest mammal. It depends on what you're describing, and what the presupposed norm in context is. So you won't find them as measurements (except comparatively) in scientific publications, where mass and weight are normally distinguished and measured in appropriate units. Nov 6, 2020 at 18:12
  • How then to come up with a single positive number for each object that reflects all of the above, etc, "apples and oranges" aspects averaged out? Nov 6, 2020 at 19:07

3 Answers 3


I often see in scientific literature the adjective "large" associated to mass/weight, such as "this animal is larger than another"

Are you sure this is what you see? I would be surprised. The default meaning for "large" when it comes to animals and most physical objects refers to overall volume (of the envelope), not to mass/weight. Of course a high volume object is often heavier than a small object but this is not inevitable.

In the following fanciful image, the balloon is larger than the elephant, even though we know that the elephant is heavier/more massive.

*envelope = a surface that surrounds the shape.

enter image description here

  • Not a good example to reflect your position that, "a high volume object is often heavier than a small object but this is not inevitable". Going skyward, the balloon is "heavier". Nov 6, 2020 at 19:09
  • Yes I am quite sure because I read these articles all the time. Any of these articles scholar.google.com/… use "large mammals" to identify mammals weighting over X amount of Kg. They never use volume measurement because measuring volume in animals is rather complex. Nor they use size measurements such head to toe length. Nov 6, 2020 at 20:13
  • @Herman Toothrot - I can see that those articles refer to large animals but I don't see where it says that large = heavy. Can you give an actual definition of large in one of these? If not, then I continue to say that "large" refers to spatial dimensions and not mass. I understand that the approximate density of animals tends to be similar and therefore, in general, larger animals are heavier but that doesn't mean that these quantities are the same. Nov 6, 2020 at 20:48
  • @Rem - "Going skyward, the balloon is 'heavier'"(?) I have no idea what that means. In relation to the atmosphere, an elephant is heavier than air and a helium balloon is lighter (not heavier) than air. Nov 6, 2020 at 20:55
  • @chasly-supportsMonica Look at this one advances.sciencemag.org/content/1/4/… "Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg)". This is in Science. I think this use of large is simply wrong but it's widespread. Nov 6, 2020 at 21:18

large (adjective)

big in size or amount

Cambridge dictionary

Hence we may speak of a balloon as large (in size) but small (in mass of membrane and gas). Or we may speak of a sandbag that is small in size but large in mass of sand.

A simple statement that something is large merely says that it is large in size. It says nothing about mass. In your example of animals, there is a general correlation between the mass and volume (size) of land animals or fish, so sloppy usage may well say the animal is large, implying that its mass is also large. But this is careless and vague unless the context already clearly relates to mass.

In scientific writing it is bad practice to use the words large or small alone when talking about anything other than size. Such careless use of terms might pass in popular writing on science but should be edited out in anything authoritative. When taking about mass, say large mass or small mass.

Also, in scientific writing it is important to distinguish between mass and weight. A mass of a kilogram weighs a kilogram in earth's gravity but weighs nothing in space.

  • I do agree with you but as I have mentioned anywhere in the scientific literature I find the use of "large" or "very large" as a proxy for weight. Look at this scholar.google.it/… . Why do you associate the concept of mass with large? For me a mass is heavy or light. Mass is measured in Kg so why would you use large/small? You don't say my backpack is large when you want to say that it's actually heavy. Large I would use it to indicate volume. Nov 6, 2020 at 20:17
  • You ask why speak of large mass? Why not? According to the dictionary definitions (and to my own experience), the adjective large applies to many things: volumes; lengths; intellects; bones; areas; mammals; faunas & extent (all as in the link you give); dresses, shirts ... so why not apply it mass? The units of mass or any other qualified noun are irrelevant: a mass of 10 kg is larger than that of 1 kg whether you measure the mass in kg, tonnes, ounces or milligrams. And I do say "large rucksack", as is shown in google ngram. If the sack is full it may be heavy; if empty it is light.
    – Anton
    Nov 6, 2020 at 22:22

The mass of an object is defined as the "amount of matter" in an object

Defining mass as "amount of matter" is garbage that is passed for science in middle school. Mass is measure of body's inertia. It is resistance to changing its velocity when a net force is applied.

Mass is measured in kilograms (in SI). Amount of matter is measured in moles (mol).

We can talk about heavy and light bodies as difference in their change of velocity under the same force. Bodies placed on Earth's surface experience the same gravitational pull, so equality of masses means equality of weights. Hence, I don't see any problem talking about "heavy" and "light" in regards to mass. Obviously, "large" does not mean "large mass", it just means large dimensions. Thus, "heavy" == "large mass".

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