A constant is a fixed value that remains unchanged within a given context.
Word in 30 Seconds
- A value that does not change.
- Used in math, science, and programming.
- Opposite of a variable.
Overview
常数（Constant）是一个在特定上下文中数值固定不变的量。无论是在数学公式、物理定律还是计算机程序中，常数都扮演着重要的角色，它们提供了一个稳定、可预测的基准。与变量（variable）不同，变量的值可以根据条件或计算过程而改变，而常数的值一旦设定，就不能被修改。
在数学中，常数常用于表示一些普遍成立的数学事实，例如圆周率 π ≈ 3.14159，自然对数的底 e ≈ 2.71828。在物理学中，常数则代表自然界的基本属性，如光速 c、普朗克常数 h 等。在计算机编程中，常数用于存储那些在程序运行期间不会改变的值，例如最大连接数、配置文件的路径等，这有助于提高代码的可读性和可维护性。
常数广泛应用于科学研究（如物理学、化学）、工程学、计算机科学、经济学等多个领域。在日常生活中，虽然不直接使用“常数”这个术语，但我们也会遇到一些固定不变的数值，例如每年的固定节假日日期、某些产品的标准规格等，这些都可以看作是生活中的“常数”概念的应用。
与“常数”最常对比的是“变量”（variable）。变量的值可以改变，用于表示不确定的或变化的量，例如在方程 x + 5 = 10 中，x 就是一个变量。而常数的值是固定的，例如方程中的 5 和 10 就是常数。在某些语境下，“固定值”（fixed value）也可以作为“常数”的近义词，但“常数”通常带有更强的数学或科学含义，而“固定值”则更侧重于其不可变性。
Examples
圆周率 π 是一个重要的数学常数。
academicThe mathematical constant Pi (π) is very important.
在编程中，我们经常定义一些常数来表示固定的配置信息。
technicalIn programming, we often define constants to represent fixed configuration information.
根据万有引力定律，引力常数 G 是一个普适常数。
academicAccording to the law of universal gravitation, the gravitational constant G is a universal constant.
这个计算器的最大值是一个常数，无法超过。
informalThe maximum value of this calculator is a constant and cannot be exceeded.
Common Collocations
Common Phrases
基本常数
fundamental constant
定义一个常数
define a constant
数学常数
mathematical constant
Often Confused With
A variable is a quantity that can change or vary, whereas a constant remains fixed. They are fundamentally opposite concepts.
A parameter is often a variable that is given a fixed value for a specific instance or calculation, acting like a temporary constant within that context. However, parameters can sometimes be changed between different instances.
Grammar Patterns
How to Use It
Usage Notes
The term 'constant' is primarily used in technical and academic contexts like mathematics, physics, and computer science. While the concept of something unchanging exists in everyday life, the specific word 'constant' is less common in casual conversation unless discussing these fields.
Common Mistakes
A common mistake is confusing constants with variables, especially in programming where understanding the difference is crucial for writing correct code. Another error might be trying to change the value of a declared constant, which leads to program errors.
Tips
Identify Fixed Values
Look for numbers or quantities that are stated as unchanging in a problem or description. These are likely constants.
Avoid Modifying Constants
In programming, attempting to change the value of a declared constant will usually result in an error. Respect their fixed nature.
Universality of Constants
Many scientific constants (like the speed of light) are believed to be universal, holding true everywhere in the universe.
Word Origin
The word 'constant' comes from the Latin word 'constans', meaning 'standing firm' or 'unchanging'. This root clearly reflects its meaning of steadfastness and immutability.
Cultural Context
In science, the discovery or precise measurement of fundamental constants is a major achievement, often leading to new understandings of the universe. Debates about whether some constants might slightly change over cosmic time are active areas of research.
Memory Tip
Think of a 'constant' as something 'constantly' the same, like a statue that never moves. A 'variable' is like a person who constantly changes their mind.
Frequently Asked Questions
4 questions常数的值是固定的，不会改变；而变量的值是可以变化的。在数学和编程中，它们用于表示不同性质的量。
虽然不常使用“常数”这个词，但像固定的节假日日期、某些产品的标准尺寸等，都体现了数值固定不变的概念。
使用常数可以使代码更清晰、易于理解，并且当需要修改这个固定值时，只需修改一处，避免了潜在的错误。
著名的数学常数包括圆周率 π（Pi）和自然对数的底 e。它们在数学和科学中有广泛的应用。
Test Yourself
在数学公式 E=mc² 中，c 代表 ____ 的速度。
c（光速）在物理学中是一个固定不变的常数。
下列哪个例子最能体现“常数”的概念？
班级人数在一段时间内保持不变，符合常数不变的特性，而其他选项都表示会变化的值。
请组合以下词语构建句子：常数，变量，区别，在于，值，是否，改变。
这个句子准确地表达了常数和变量的核心区别。
Score: /3
Summary
A constant is a fixed value that remains unchanged within a given context.
- A value that does not change.
- Used in math, science, and programming.
- Opposite of a variable.
Identify Fixed Values
Look for numbers or quantities that are stated as unchanging in a problem or description. These are likely constants.
Avoid Modifying Constants
In programming, attempting to change the value of a declared constant will usually result in an error. Respect their fixed nature.
Universality of Constants
Many scientific constants (like the speed of light) are believed to be universal, holding true everywhere in the universe.
Examples
4 of 4圆周率 π 是一个重要的数学常数。
The mathematical constant Pi (π) is very important.
在编程中，我们经常定义一些常数来表示固定的配置信息。
In programming, we often define constants to represent fixed configuration information.
根据万有引力定律，引力常数 G 是一个普适常数。
According to the law of universal gravitation, the gravitational constant G is a universal constant.
这个计算器的最大值是一个常数，无法超过。
The maximum value of this calculator is a constant and cannot be exceeded.
Related Content
Related Vocabulary
More academic words
缺席
B1The state of being absent from a place or event where one is expected to be, such as a class, meeting, or ceremony.
抽象的
A2Abstract.
抽象地
B1In an abstract manner; conceptually.
艰深
B1Profound; abstruse; recondite.
学术性
A2Academic; scholarly; relating to education and scholarship.
学术化
B1Academic; characterized by formal study or research.
学术会议
A2Academic conference; a formal meeting for academic discussions.
学术交流
B1Exchange of ideas, information, and research among scholars.
学术期刊
B1A periodical publication containing scholarly articles.
教务处
A2Academic affairs office; department handling educational administration.
