'Much' is used to describe a relative amount of a noun that can't be easily counted or quantified. If you can't put a number before the noun, use 'much. '
Much is often combined with a modifier like 'too, ' 'not, ' or 'very. '
'Many' describes a quantifiable, countable noun. If you can put a number before the noun you should probably use 'many. ' Here if you replace the object with a pronoun, it will be plural (them, they).
In most cases, either one works fine, but you should be careful about replacing 'a lot' or 'lots' with 'many' or 'much. ' Note that in the examples below 'many' works in place of 'lots/a lot', but 'much' doesn't work at all.
The difference between much and many is basically about countable and uncountable.
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