Prefixes -ex and -in

The prefixes -ex and -in combine with roots to form many English words. In many cases the word pairs with these two prefixes have opposite meanings. Here's a list of ten words:

ejection injection
emigration immigration
exception inception
excitement incitement
exclusion inclusion
excursion incursion
exhalation inhalation
explosion implosion
expression impression
exportation importation

The word pairs ejection/injection, exclusion/inclusion, excursion/incursion, exhalation/inhalation, explosion/implosion and exportation/importation truly reflect the meaning of the prefixes. For example, exhalation is the action of breathing out and inhalation is the action of breathing in.

In the word pair emigration/immigration, the first word focuses on the point of departure and the second on the point of arrival. The word pair exception/inception doesn't appear to be so closely related. The word exception refers to a circumstance that doesn't conform to a particular rule and inception means beginning. In the case of expression/impression, the former communicates thoughts and ideas and the latter is an idea or feeling formed without conscious thought. The word incitement refers to the action of provoking unlawful behaviour and excitement is the feeling of pleasure.

The prefixes -ex and -in changed in certain words because of assimilation and deletion. We can illustrate the changes as follows:

ex + jection = ejection
ex + migration = emigration
in + migration = immigration
in + plosion = implosion
in + pression = impression
in + portation = importation

English has many words with the prefixes -ex and -in. These prefixes have variants because of assimilation and deletion. The prefix -in becomes -im before a p and -ex becomes -e before an m.