What is the difference between "undemonstrable" and "indemonstrable"? Indemonstrable has the meaning whereas the undemonstrable doesn't have. According to Google NGRAM both the words are widely used but Merriam webster or Oxford Dictionary doesn't provide the meaning.
Which word is correct "undemonstrable" or "indemonstrable"? Do they have same meaning?
EDIT: This is what I got when I searched in Merriam-webster.
And for Oxford dictionary
Demonstrable just happens to be one of those words that doesn't have a well-established negating prefix (both un- and in- are used, with exactly the same meaning). But as this chart shows, native speakers don't much like either form - perhaps partly because of that uncertainty. We're much more likely to use alternative phrasing...
It may be worth comparing the full OED entry for...
indemonstrable
...and...
undemonstrable
Apart from the smaller number of citations, it may be significant that OED don't even bother to give the pronunciation for the latter (which has mostly been less common over the past two centuries).
The prefixes "in" and "un" are defined in most dictionaries. In both the Oxford and the American Heritage dictionaries they are both defined as "not or the opposite of". Therefore "undemonstrable" and "indemonstrable" mean the same thing. The only difference between "in" and "un" is that "in" can be used with "adjectives and words formed from adjectives" and "un" can be used with "adjectives, adverbs, verbs, and nouns".
