Why are not infamous and inflammable the opposite of famous and flammable, like incomplete, inactivity, inappropriate and so on?

  • 11
    What, inflammable means flammable? What a country! Commented Dec 15, 2010 at 12:59
  • 11
    English is both ingenious and intuitive; however, the genious and tuitive among us must struggle along.
    – rajah9
    Commented Jan 10, 2014 at 21:08
  • 1
    Also: invaluable
    – Benubird
    Commented May 1, 2014 at 14:22
  • 2
    It needs to be noted that "flammable" is effectively a neologism, having been popularized ca 1960 because of the confusion (in the US , at least) as to the meaning of 'inflammable". "Non-flammable" is the corresponding antonym.
    – Hot Licks
    Commented Nov 8, 2017 at 12:54

3 Answers 3


The New Oxford American Dictionary I had on my Mac Mini (which was the third edition, last time I checked) reported the following definitions for in-:

in- 1
1. (added to adjectives) not: inanimate | intolerant.
2. (added to nouns) without; lacking: inadvertence | inappreciation.

in- 2
prefix in; into; toward; within: induce | influx | inborn.

Looking at the origin of infamous, and inflammable, I read the following:

ORIGIN late Middle English: from medieval Latin infamosus, from Latin infamis (based on fama 'fame').

ORIGIN early 17th century: from French, or from Latin inflammare (see inflame).

In both the cases, the words are not built adding the prefix in- to existing words.

  • 3
    but I could argue that they are indeed built by adding the suffix in- to existing words :)
    – user733
    Commented Aug 22, 2010 at 22:15
  • 11
    You are right user733 (except that it is a prefix, not a suffix). They are actually built using the prefix in- (even if English borrowed the whole word including the prefix). It is just that there are two prefixes that look like "in", and both came from Latin, and both were the source of these two words we borrowed. In both cases it is in #2 from kiamlaluno's NOAD quotation. This morpheme in is etymologically the same in that the English prefix en comes from, in words like "enable", "enclose", "encrypt", etc.
    – Kosmonaut
    Commented Aug 23, 2010 at 3:25
  • 11
    Just to confuse things even more, in french the word for nonflammable is ininflammable, with the two different prefixes used one before the other.
    – ogerard
    Commented Apr 24, 2011 at 7:11
  • 3
    That is exactly what happens in Italian, with ininfiammabile.
    – avpaderno
    Commented Feb 21, 2012 at 23:35
  • This doesn't explain the meaning of the prefix in- in the context of infamous. Commented Nov 4, 2023 at 10:59

(Just to be contrarian.)

  1. The word infamous is the opposite of famous! Just as the opposite of reputed is disreputed rather than obscure, and the opposite of hot is cold rather than not hot, the opposite of famous (having "good" fame) is infamous (having "bad" fame, having infamy, ill-famed).

  2. The word "flammable" is newer than inflammable and does not exist, for instance, in Indian English. Historically, the only word was inflammable, dating to at least the 16th century. "Flammable" did not exist. Note that we still say inflammatory speeches not *flammatory speeches, inflammation of the skin not *flammation of the skin, etc. (However, flammation "exposure to fire" actually exists in the OED and is marked as obsolete, the only quote dating to 1646.)
    The word "flammable" was invented around 1813, but it didn't catch on, and some time in the 19th century was pretty much dead: The 1913 Webster's dictionary marks the word "flammable" as obsolete. Unfortunately (IMHO), this word was revived after World War II. (See this letter. More precisely, the word flammability was revived, and then "flammable" followed.)
    The OED entry for flammability is:

flammaˈbility, n.
= inflammability n. Revived in modern use to avoid the possible ambiguity of inflammability, in which the prefix in- might be taken for a negative (in- prefix3).

In my opinion, the word flammable was unnecessary: there's not much confusion possible in seeing, on a gas/petrol tanker, the words "Warning: Highly inflammable". It seems to me there's more confusion about the meaning of inflammable when the word "flammable" exists, than when it doesn't. But where "flammable" is already common enough, it's safe—and recommended—to use it.

  • 3
    Hot and Cold are on a spectrum where it can be logically said that the opposite of one end of the spectrum is its counterpart at the other end equidistant from some midpoint of that spectrum. Famous and infamous are not the same; both are famous but one is good fame and one is bad fame. I don't think it really makes sense to talk about them in terms of "opposites". Commented Feb 9, 2012 at 19:24
  • 2
    It's more of a two-dimensional spectrum: One dimension for well-known vs. obscure, and one dimension for +ve vs. -ve.
    – Dan
    Commented Oct 20, 2012 at 23:29
  • 1
    Your reputed example works, but I'm also not sure about hot vs cold. The question is about how the modifier -in has two different senses - you don't really say un-hot or in-hot or dis-hot at all, regardless of whether or not it means something other than cold.
    – Hannele
    Commented Jun 14, 2013 at 16:05
  • 1
    But an opposite of famous is unknown. It's not a midpoint on a scale between famous and infamous, because you can be both very good and very bad at something, and also not be very well known for it. The fact that infamous has a meaning other than unknown highlights that there are two different opposites - similarly, disreputed meaning something other than not having reputation.
    – Hannele
    Commented Jun 14, 2013 at 17:40
  • 1
    Yes! And I am saying that famous has two opposites - both infamous and unknown - and each has a different meaning. Consider how politics - often divided only into left and right-wing - can also be described by authoritarian vs liberal, where there are both authoritarian left-wingers and liberal right-wingers. There is more than one opposite, and they mean different things.
    – Hannele
    Commented Jun 14, 2013 at 21:01

The folklore with the term "flammable" was that it had to be invented precisely because people read "inflammable" as "won't burst into flame" (and granted, "inflame" really isn't a word you get to hear everyday). The blame should be apportioned to the safety people I suppose. :)

  • 15
    Ultimately, it means that no company or person should ever use the word inflammable under any circumstances, because in any situation where it is crucial enough to mention, you don't want to leave any doubt :) Stick with flammable and nonflammable.
    – Kosmonaut
    Commented Aug 23, 2010 at 12:39
  • 4
    On a personal note, "flammable" grates on my ears. :) If I were to address a bunch of foremen and construction workers, however, I would grit my teeth and say something like "paint is flammable!"
    – user730
    Commented Aug 23, 2010 at 13:02
  • 2
    Good point. At least the words has gotten me some free beers from bets over the years. As a country of good english language education, everyone know about the prefix in- to reverse the meaning. Most people who just rely on logic are flabbergasted when they look it up and realize their defeat... =)
    – user733
    Commented Aug 23, 2010 at 16:30
  • 4
    Somewhat related: The U.S. Navy does not use the word unload (take cargo out of a ship) because in can be confused with onload (put cargo aboard a ship). Rather, only the words load and off-load are used.
    – cobaltduck
    Commented Dec 1, 2011 at 21:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.