The action of grouping things together; a cluster or collection of grouped items.
From 'aggroup' plus the suffix '-ment.' Created by adding the French-derived suffix to form a noun describing the result of grouping action, following standard English word-formation patterns.
This word exemplifies how English can manufacture words from its existing pieces—even if nobody really uses 'aggroupment,' the '-ment' suffix is so productive that technically any verb can become a noun this way, and that's why English has such a vast potential vocabulary.
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