What is the difference between a countable and an uncountable noun? Provide examples.

Countable and uncountable nouns are two categories used to classify nouns based on their ability to be counted or measured. The main difference between them lies in their usage and the way they interact with determiners, quantifiers, and verbs.

Countable nouns refer to objects or concepts that can be counted as separate individual units. They have both singular and plural forms and can be preceded by numbers or quantifiers. Examples of countable nouns include "book" (books), "chair" (chairs), "dog" (dogs), "student" (students), and "apple" (apples). Countable nouns can be used with the indefinite article "a" or "an" before the singular form and with the definite article "the" before both singular and plural forms.

Uncountable nouns, on the other hand, represent substances, concepts, or qualities that cannot be counted as separate units. They are usually treated as singular and do not have a plural form. Uncountable nouns cannot be preceded by numbers or used with "a" or "an." Instead, they are often accompanied by quantifiers such as "some," "any," "much," or "a lot of." Examples of uncountable nouns include "water," "information," "furniture," "advice," and "happiness."

To further illustrate the difference, consider the following examples:

1. Countable noun: "I have two books on my shelf."
In this sentence, "books" is a countable noun that can be counted and has a plural form.

2. Uncountable noun: "I need some water to quench my thirst."
Here, "water" is an uncountable noun that represents a substance and cannot be counted or have a plural form.

3. Countable noun: "She has three dogs as pets."
"Dogs" is a countable noun that can be counted and has a plural form.

4. Uncountable noun: "He gave me some advice before the interview."
In this case, "advice" is an uncountable noun that represents a concept and cannot be counted or have a plural form.

In summary, countable nouns can be counted and have both singular and plural forms, while uncountable nouns cannot be counted and are usually treated as singular.