A non-standard or erroneous plural form attempting to pluralize criterion in English, rather than using the correct form 'criteria.'
A blend of Latin 'criterium' with English pluralization ('-ons'), resulting from uncertainty about proper Latin plural conventions.
When speakers invent 'criteriions,' they're showing the eternal tension between Latin grammar and English stubbornness—English wins eventually, but not without producing strange hybrids first.
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