The magic of IN

[ghanashyam]

In English, generally the IN is used as prefix to change the word. Like say, CAPABLE vs INCAPABLE, FORMAL VS.INFORMAL but see FLAMMABLE  is not vs INFLAMMABLE

Do you know any such words ? Put them here.

[thekernel]

Do you mean prefixes that alter the word to mean the opposite? Because some words use "a" or "un" to achieve a similar effect. "Tonal" vs "Atonal" or "Believable" vs "Unbelievable" for example.

Or do you mean other words that "In" can be added to, i.e. "Insufferable", "Insatiable", or "Incongruent"?

[LauraM]

In English, generally the IN is used as prefix to change the word. Like say, CAPABLE vs INCAPABLE, FORMAL VS.INFORMAL but see FLAMMABLE  is not vs INFLAMMABLE

Do you know any such words ? Put them here.

Great topic! Typically the prefix "in" means "not."  In other words, it will convey the opposite meaning such as in your examples.

But there are some exceptions, as you noted.  "inflammable" actually means something that can be set on fire easily. 

As for words that do follow the rule, of creating the opposite meaning we have for instance:

"Dependent" vs "independent"

"Flexible" vs "inflexible"

"Mutable" vs "immutable"

"Tolerant" vs "intolerant"

And there are many more.

[limon]

What bugs me is when it seems like there should be a pair to an 'in' word, but there isn't. Like 'inept'.

[thekernel]

What bugs me is when it seems like there should be a pair to an 'in' word, but there isn't. Like 'inept'.

I believe the antonym counterpart to that would be "adept". As with most rules in English, there are several exceptions that can defy logic -- the logical application of the prefix would indicate that the word should be "inadept". And of course, sometimes the first two letters of the word can just happen to be "IN" and not a use of the prefix, like "index" or "inane".

[limon]

I believe the antonym counterpart to that would be "adept".

That makes perfect sense. But I'm going to continue using the 'ept' out of sheer stubbornness ;D

[Alfonso]

I understand the usage of in,that it basically mean "not", does that go the same for im

proper - improper

mobile - immobile

possible - impossible

potent - impotent

polite - impolite

[BWL]

I agree, this is very productive in English but not exceptionally so, depending on the Latin loanword it was taken from. You can say "insidious" but not "sidious". You can say "instigate" but not "stigate".

[pandandesign]

Great topic! Typically the prefix "in" means "not."  In other words, it will convey the opposite meaning such as in your examples.

But there are some exceptions, as you noted.  "inflammable" actually means something that can be set on fire easily. 

As for words that do follow the rule, of creating the opposite meaning we have for instance:

"Dependent" vs "independent"

"Flexible" vs "inflexible"

"Mutable" vs "immutable"

"Tolerant" vs "intolerant"

And there are many more.

Great response! "In" does mean more than a prefix "not". It depends on the words actually. For instance, Instruction doesn't mean it's opposite to a structure or something. I means a guideline or a set of rules that people should follow. 

[justusforus]

Back to the "in" words

efficient - inefficient

tolerable-intolerable

sufferable-insufferable

I can't think of more the rest have said...but I know there is a lot

[rodserd]

Learning latin prefixes is very helpful in learning English.  however, you cannot rely on them 100%

[lovemwaf]

The use of the prefix in for me has always been natural and I have not really ever had to to think about it's application.....words such as inconvenience have never really appealed to me as a combination of words

[kilat]

I understand the usage of in,that it basically mean "not", does that go the same for im

proper - improper

mobile - immobile

possible - impossible

potent - impotent

polite - impolite

Yes, the "im-" prefix is simply a form of "in-" that has come to be pronounced and written that way because it's easier to say. Try saying "inproper", "inmobile" or "inpossible" and you'll understand why! Whether it's "in-" or "im-" basically depends on the consonant that comes after the prefix in each word, and how people tend to pronounce the word. Like many other aspects of language, spellings and common pronunciations can change over time, so some of these words might actually have had different spellings centuries ago.

[Daimashin]

Interesting topic. I've always had problem differentiating when to use un, in, and im for words of the opposite meaning. After reading the posts, some of it are clear to me.

[LivetoErr]

In- changes to Im- when the root word begins with a m or p. So, for example, mobile becomes immobile and possible becomes impossible.

In- can mean not, with or into. So, for the original posters example of flammable vs. inflammable - inflammable does mean it is not flammable. Flammables can cause a fire, inflammables cannot.

Basically, when you're adding In- to a word in order to make the word mean 'not' something follow these rules:

In- changes to Il- when the root word begins with L, i.e, logical/illogical

In- changes to Ir- when the root word beings with R, i.e, reversible/irreversible

In- changes to Im- when the root word begins with M or P, i.e, mortal/immortal, personal/impersonal

There are words, however, that simply have In- in them. For example, interest; the proper way to express the opposite of interest would be by adding the suffix, dis-. His disinterest in the lecture was maddening.

If you're having trouble with prefixes, use Google. There are lots of search results that can help you.