The words entrepreneur, nuance and opportunity are names that represent real and abstract things; these words are called nouns. It would be boring, however, if writers and speakers could only name things and not describe them with words such as brilliant, hidden or life-changing. These latter words are adjectives and describe nouns. There are many differences between nouns and adjectives. Comparing their definitions, whether or not they are counted, and the degree of dependence they have on each other reveals how they are fundamentally different.
A noun names a person, animal, place, thing, quality, idea or action. "Kiwi," for example, is a noun that names a specific fruit and "democracy" names a specific form of government. Adjectives describe the quality, quantity, extent or distinction of a noun. When an author refers to a representative democracy, "representative" is being used as an adjective because it distinguishes a type of "democracy." When "representative" is used to name a person -- the school representative -- it is functioning as a noun.
Nouns and Counting
Some nouns name things that are countable. If the countable noun names something of which there is only one, it is referred to as singular; if it names more than one thing, it is referred to as plural. Groups can be confusing because if the group is being referred to as a unit, it is singular -- "my family is going to the store." If each member of the group is being referred to, then it is plural -- "the data are being plotted as individual points on a graph." Other nouns that cannot be counted, like butter, are mass nouns. Mass nouns are considered singular.
Adjectives and Counting
An adjective can be used to describe how many of a countable noun or how much of a mass noun exists. Furthermore, the type of adjective used can depend on whether it is describing a count noun or mass noun. "Many" and "fewer," for example, are used with count nouns such as "ideas" and "much" and "less" are used with mass nouns such as "motivation" -- "I have many new ideas, and yet I still I have less motivation."
A noun can be used without an adjective -- "She ran home." -- but an adjective can modify it. An adjective must have a noun to modify. Even "Excellent!" implies that something is excellent. To determine if a word is an adjective or a noun, determine its function. Finally, adjectives and nouns do not have to appear next to each other to retain their roles: "Beautiful Kimiko" might be expressed as "Kimiko is beautiful." "Beautiful" is the adjective in both cases and "Kimiko" is the noun.