81
Definition
- Adjective:
- Being one more than eighty: The number 81 is the natural number that follows 80 and precedes 82. It is represented by the numerals '81' or the Roman numeral 'LXXXI'.
Usage
- The word '81' is a cardinal number used for counting, ordering, and labeling. It functions primarily as an adjective when it modifies a noun to indicate quantity or position.
- The book has 81 pages. (It modifies the noun "pages" to specify the quantity.)
- She finished in 81st place. (Here, the ordinal form "81st" indicates position in a sequence.)
Examples
- Adjective:
- The temperature reached 81 degrees Fahrenheit today.
- He scored 81 points in the basketball game.
- The project will take 81 days to complete.
Advanced Usage
- As a numeral in mathematics: 81 is a perfect square (9²), a perfect fourth power (3⁴), and the sum of the first nine prime numbers (2+3+5+7+11+13+17+19+23).
- The square root of 81 is 9.
- In cultural or historical contexts: The number may be used symbolically or refer to specific years, ages, or identifiers.
- He was born in '81. (Referring to the year 1981 or 1881, depending on context.)
Variants and Related Words
- Eighty-one: The word form of the number.
- 81st (eighty-first): The ordinal number form.
- LXXXI: The Roman numeral representation.
Synonyms
- Eighty-one: The literal synonym in word form.
- Four score and one: An archaic phrasing (from "four score" meaning eighty).
Related Phrases
- Chapter 81: Used to label a specific section in a book or document.
- Route 81 / Highway 81: Used in the names of roads or highways.
- 81 years old: A phrase describing age.
Adjective
-
being one more than eighty
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