Learn English – grammar rule for prepositions

prepositions

What is the grammar rule for the preposition after the word free? Why do we say free of impurities but free of charge?

Best Answer

The "charge" vs. "impurities" difference you actually seem to be asking about is nothing to do with the preposition as such; it's to do with "charge" being a "mass noun", so not calling for pluralization, and "impurity" being a "count noun", which it's appropriate to pluralize here.

This distinction is the same one as produces the "less vs. fewer" dichotomy.

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