English has many different ways to answer the question "how much?" or "how many?" — and choosing the right one depends on a few key factors: whether the noun can be counted, how large or small the amount is, and how precise the speaker wants to be.
At the most basic level, quantity can be expressed through:
Quantifiers — words like many, much, few, little, some, any, all — that describe an amount without stating an exact number.
Numbers and measurements — expressing a precise quantity, either directly (three books) or through units for things that can't be counted individually (a bottle of water, a piece of advice).
Degree words — expressing quantity applied to qualities or actions, rather than nouns (very tired, too fast, enough time).
Each of these tools follows its own rules, and many of them depend on one key distinction we'll cover first: whether the noun being quantified is countable or uncountable.