The Latin plural of the noun apparatus is actually apparatus (the vowel lengthens, but that's not reflected in the spelling). The English plural is apparatuses. You don't actually hear the English plural apparatuses that often, because apparatus is treated as a semi-uncountable noun: one apparatus, two pieces of apparatus. "Apparati" is incorrect in either language.
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The plural form of apparatus is apparatuses. It has no foreign plural.
The plural form of plastic is plastics.
The plural form of building is buildings.
The plural form is technologies.
The plural form for the noun 'material' is materials.