Grammatically speaking, what are countable nouns and noncountable nouns & how are they different?

Answer 1

Good explanation Ryah,except that concepts/ideas/abstracts are not mass nouns. ie. love, hate, electricity, democracy... Mass nouns or group noun examples follow:

Here's another way - A group (uncountable) and it's components (countable). ie. Money (group meaning all) the components are cents, nickels, dimes, quarters, dollars... Furniture (group meaning all) the components are tables, chairs, beds, sofas...

Liquids are uncountable BUT you can count the containers it's in. ie. 1/2/3/4 cups. Rice, Sugar (well you could count them if you had nothing else to do), coffee are also uncountable and are counted by the containers.

So, it's not that difficult if you think about it.

Answer 2

Counting nouns are nouns that can take a plural form, can combine w/ numeral or other quantifying adjectives (like two, several, many) or can be used with an indefinite article (a or an) such as dog, tree, pencil.

Noncountable nouns (aka mass nouns) are words that do not have to be used with an indefinite article or quantifying adjective - words like creativity, politics, plutonium, etc.. You would never say, "I have a creativity". These words may be mass, but they do not have plural forms.