What is the relationship between the words ductile and malleable? They are definitely not antonyms, but can we call them synonyms?

  • 2
    They are not synonyms. They are two distinct physical properties of materials. en.wikipedia.org/wiki/Malleability Oct 18, 2013 at 18:07
  • Actually, they are similar, but not necessarily synonyms. Check my response for an explanation.
    – Cindy Page
    Oct 18, 2013 at 18:28
  • They're both borrowed a long time ago from Latin. Ductility means 'leadability', from the verb ducere 'to lead'. Malleability means 'hammerability' from the noun malleus 'hammer'. That's the source, retained for millennia, of the respective 'stretching' and 'compressive stress' senses for the two words. They are not synonyms; they're related, but English doesn't have a term for the relationship. Feb 1, 2022 at 15:08
  • It's the suffixes: ile and able which make them "relatable".
    – Lambie
    Feb 1, 2022 at 17:56

5 Answers 5


Both words indicate an item can be shaped, as in metal or plastic, but you would not say a child's mind is ductile, because you don't hammer at a child's mind, or heat it to mold it into shape. Malleable is a more flexible word.

Ductile has the property of physical shaping, while malleable has the property of formation. Malleable can include shaping by force, as in using a mallet. But malleable also could allow change through influence or subtle alteration as opposed to force: The child is malleable, so be careful what you teach him. Ductile allows only physical change of shape: I must heat the plastic to make it ductile.

Ductile is also related to the word viscous or viscosity, because a solid that flows is ductile. Viscous lava can be shaped through physical means, but the more viscous it is, the less fluid the lava is, and the more force required to change its shape. So highly viscous fluid is less ductile than low viscosity lava. Low viscosity lava is malleable. (Easily shaped.) High viscosity lava is ductile. (Resistant to shaping, but it is possible to use force or its physical properties to make it easier to shape a ductile material.)

  • This does not answer the question, which is "Relationship between "ductile" and "malleable" ... a word to describe words related like this".
    – Greybeard
    Feb 1, 2022 at 16:53

see the Wikipedia entry on ductility.

[D]uctility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. ... Malleability, a similar property, is a material's ability to deform under compressive stress.

  • What's with the square brackets in [d]uctility? Are you implying uctility (and presumably, uctile) are valid alternatives to ductility/ductile? I never heard of this. Oct 19, 2013 at 18:12
  • 1
    @FumbleFingers the original has a lowercase d.
    – user31341
    Oct 20, 2013 at 15:03
  • Intriguing. I sometimes do this myself when swapping proper nouns for pronouns (or vice-versa) in citations, but it wouldn't occur to me to do it for a letter-case switch. In fact, I'm so intrigued I've asked a question about it Oct 20, 2013 at 17:19
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    I am well aware of the definition. Please answer the question. I know they are similar. But can we call them synonyms? Oct 21, 2013 at 15:31
  • @AmanMathur it seems like what you are interested in is the definition of "synonym". Ask that question directly on Linguistics.SE.
    – user31341
    Oct 23, 2013 at 23:51

Franklin of 'Wordmaster' fame calls 'words related by subject' (which obviously includes synonyms, and perhaps antonyms) Classmates™. Since 'classmate' dates back to 1705-15 (RHKWebster's), I'm not sure how they can trademark the word or a novel sense of an existing word. The obvious places to look for them are in thesauri and glossaries.


Ductility and malleability are obviously related - they both refer to how much a metal can be modified by working it. They are not identical, i.e. not synonyms, because the first is how well it is modified when pulled (under tensile stress), the second when pushed (under compressive stress).

But they are not opposites, no antonyms, because they are independent - a metal can be ductile or not, and separately it can be malleable or not (with four possibilities). Yes, a ductile metal tends to be malleable and vice versa, but there's no guarantee - there are ductile materials that are not very malleable, and malleable ones that are not very ductile.

Hot and cold are antonyms, and hot and boiling are synonyms. These words are all on the same dimension.

But height and weight are on two separate dimensions. They are correlated - the taller a thing is, the heavier it tends to be. There are tall things that are light and heavy things that are short.

Ductile and malleable are more like tall and heavy than hot and boiling. They are not on the same scale.

Then what do you call the relationship between the two. There's no official single word for it but there are a number of ways to describe it more succinctly. Ductility and malleability are highly correlated independent variables, or to take the end point adjective of each dimension, ductile and malleable are highly correlated (and that they are on different dimensions is implied by the use of 'correlated'). If the variables were uncorrelated (you couldn't predict one from the other), then they are just two different variables or for the adjectives, they are just unrelated.


Relationship between "ductile" and "malleable" ... a word to describe words related like this

They are attributes



4.a. A quality or character considered to belong to or be inherent in a person or thing; a characteristic quality.

Copper Attributes: Copper is… A preferred electrical conductor, an excellent thermal conductor, antimicrobial, durable, ductile

Or properties

b. An attribute, characteristic, or quality. In earlier use sometimes: a distinctive, essential, or special quality; a peculiarity.

(a) Of a thing.

1832 D. Brewster Lett. Nat. Magic i. 5 The property of lenses and mirrors to form erect and inverted images of objects.

1868 J. N. Lockyer Elem. Lessons Astron. (1879) vii. xli. 241 It is one of the properties of a triangle that the three interior angles taken together are equal to two right angles.

1911 E. Rutherford in Jrnl. Soc. Chem. Industry 30 662/2 Chemical properties very similar to those of barium.

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