When to use un-, im-, or in-? [duplicate]
adverbs like inefficient, inexpensive, unnbelievable..., imbossible
Is there any roule? When to use? What to do
Solution 1:
There isn't really a rule of thumb for these. At the very least, you could say that im- is used when the adjective starts with a consonant and in- when it starts with a vowel, but that doesn't help with un-. So I suggest you memorize which prefix is correct for each case.