Quantitative adjectives modify nouns by showing how many, how much, or what proportion is involved. They usually appear before the noun and help the listener identify the size or scope of the noun phrase, just as other adjectives do in English adjective placement. They work with countable nouns, uncountable nouns, or both, depending on the word.

Cardinal numbers express exact quantity and usually come before a noun to count people, things, or units. With countable nouns, they take plural nouns after numbers greater than one, while one normally appears with a singular noun. These forms are the basic counting pattern in English and connect closely to Adjective Placement.

Idea	Example
One marks a single countable noun.	One book is on the table.
Higher cardinal numbers take plural countable nouns.	Three chairs are in the room.
Cardinal numbers normally appear before the noun.	Five students arrived early.

Ordinal numbers show order or rank, such as first, second, and third. They are placed before nouns when they function as modifiers, and they often appear with definite reference in a sequence or ranking. Ordinals behave like other adjective forms discussed in Adjective Formation.

Idea	Example
First shows the initial position in a sequence.	The first train leaves at noon.
Second shows the next position after the first.	She found the second key.
Ordinal numbers usually come before the noun.	Their third attempt worked.

Basic quantifiers describe indefinite amounts when exact counting is not needed. Many and few normally work with countable nouns, while much and little normally work with uncountable nouns. Some, any, several, and various show general amounts, and they are common in the patterns explained in Indefinite Adjectives.

Idea	Example
Many is used with countable nouns.	Many apples were left.
Much is used with uncountable nouns.	Much water was lost.
Few and little show a small amount.	Few cookies remained.
Some and several show an indefinite amount.	Several friends called yesterday.

Partitive expressions measure a noun through a larger unit, often with of after the quantity phrase. A piece of, a cup of, and a lot of are common patterns that package the noun into a measurable part or container. A couple of is also used, but its meaning is often vague and depends strongly on context and register.

Idea	Example
A piece of measures a whole by parts.	A piece of cake was left.
A cup of measures by container.	A cup of tea is ready.
A lot of shows a large amount or number.	A lot of people waited outside.
A couple of is vague and context dependent.	A couple of days felt short.

Fraction and proportion terms express parts of a whole, including half, quarter, and percent. They are used before nouns to show division, share, or rate, and the noun form depends on whether the noun is countable or uncountable. These expressions often behave like measurement phrases rather than ordinary descriptive adjectives.

Idea	Example
Half shows one of two equal parts.	Half the meal was cold.
Quarter shows one of four equal parts.	A quarter of the cake was eaten.
Percent shows a proportion out of one hundred.	Ten percent of the class was absent.

The number of the noun determines the verb form in the clause that follows the quantity phrase. Singular nouns take singular verbs, while plural nouns take plural verbs, even when the quantity expression is the subject. This agreement pattern is especially important after phrases with number of, amount of, and similar measurements.

Idea	Example
Singular nouns take singular verbs.	One student is ready.
Plural nouns take plural verbs.	Three students are ready.
Quantity phrases follow the noun number in agreement.	A number of guests are waiting.

Quantity adjectives usually come before determiners and other adjectives when they modify a noun phrase. In longer noun phrases, the quantity word is typically the first element inside the modifier group, followed by descriptive adjectives and then the noun. This ordering works with the placement principles taught in Adjective Placement.

Idea	Example
Quantity words usually come before other modifiers.	Three small boxes were delivered.
The quantity phrase normally comes before the noun.	Several old houses were sold.
Quantity expressions can stand before determiners in set patterns.	A lot of the water disappeared.

Number of is used with countable nouns, while amount of is used with uncountable nouns. These are fixed collocations, so the noun type determines the correct phrase rather than the speaker's intended meaning alone. Informal speech sometimes extends less to countables, but standard usage keeps less with uncountable nouns and fewer with countable nouns, a distinction that supports the patterns in Comparative Adjectives.

Idea	Example
Number of matches countable nouns.	The number of students increased.
Amount of matches uncountable nouns.	The amount of rain was high.
Fewer is the standard form with countable nouns.	Fewer cars used the road.
Less is the standard form with uncountable nouns.	Less noise helped everyone sleep.

Comparatives and degree words modify quantity by showing increase, decrease, sufficiency, or excess. More and less compare amounts, enough marks sufficiency, and too marks excess, with the noun form still controlling agreement and the choice between countable and uncountable patterns. These forms are closely connected to the adjective system and to Superlative Adjectives.

Idea	Example
More shows a greater quantity.	We need more chairs.
Less shows a smaller quantity.	There is less sugar today.
Enough shows sufficient quantity.	There is enough time.
Too shows excessive quantity.	Too many cars blocked the gate.

Quantitative adjectives show exact numbers, order, general quantity, proportion, and degree, and they usually appear before the noun they modify. Their form and agreement depend on whether the noun is countable or uncountable, singular or plural, and some phrases require fixed collocations such as number of and amount of. When these patterns are used together, quantity comes before the noun phrase, but the noun itself still controls the grammar that follows.