What are the reasons for double consonants?

Question

What are the reasons for double consonants in these words:

illegal
illegible
immature
irregular
irresponsible

Answer 1

The prefix il means not. With legal the l is doubled twice. Same with im- and ir-

Answer 2

The second letter in the Latin prefix in- usually changes to match the initial consonant of the adjective being prefixed if the consonant is an m, r, or l.


(Below here is a long background explanation with comparison and examples.)

Many languages have shifts of this sort, to avoid creating pronunciations or spellings that feel unnatural or misleading to their speakers. In English, for example, the regular past tense is formed by appending the sound "d", "t", or "uhd", depending on the sound terminating the verb stem:
1. If the verb ends in a vowel or voiced soft consonantal sound:
...."d": billed, booed, banned, buzzed
2. If the verb ends in an unvoiced soft consonantal sound:
..."t": bossed; boxed
3. If the ver bends in a hard consonantal sound (a stop):
..."uhd": bounded, "batted

The difference here is that the phoneme shift with the Latin prefix "in-" is correctly mirrored by a spelling shift, whereas the phoneme shift in the English past tense is not signaled by a spelling shift.

Answer 3

The first belongs to the prefix, the second is part of the root word

Answer 4

To get even with the foreigners that use 3 vowels in a row!!! LOL!

(that was a joke, get over it! LOL!)