'er' is not always inflectional
For example: teacher, dancer, worker, partner
The 'er' is not comparative in those examples, and therefore it is classified as a DERIVATIONAL suffix.
taller, nicer, bigger, lower, higher
INFLECTIONAL suffixes
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Ish, ic, al, re, im, il
childish
economic
industrial
rejoin
impolite
illogical
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