A variant or alternative form of additament; something that is added.
From Latin 'additum' (that which is added) + '-ment' (suffix for result/object). This rare variant uses the '-ment' suffix instead of '-mentum,' showing dialectal or specialized usage.
Additiment is so rare that even many English dictionaries question whether it's a real word or just a typo from old texts! It's a perfect example of how languages generate variations, and sometimes those variations just don't catch on.
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