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Questions tagged [notation]

Questions on the meaning, history, and usage of mathematical symbols and notation. Please remember to mention where (book, paper, webpage, etc.) you encountered any mathematical notation you are asking about.

Before asking a question on the site, please check if you can find your answer in Earliest Uses of Various Mathematical Symbols or the book A History of Mathematical Notations.

Alternatively, a textbook or paper usually takes the time to explain the notation they're using; please remember to mention where you've seen the notation you are asking about.

12848 questions
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Does this operator exist already?

Is there any pre-established operator or function that is zero if any of its operands is zero, otherwise negative if any of its operands is negative, otherwise positive? The sign is the most important thing here; the magnitude (in the non-zero case)…
Damien
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Notation of $\partial$

What are concepts that are generally notated by $\partial$? I know two things that are denoted by $\partial$. Those are "the boundary of a set in a topological space" and "partial derivatives". What are other concepts generally notated by…
Rubertos
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Notation for extracting the index of an element from a set

OK I edited the question. Sorry for the wrong terms. What is the correct notation such that a specific function maps an element of a specific sequence/list/n-tuple to its index? I have researched about index sets but it only gives index to a set and…
Richeve Bebedor
  • 219
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What does $\mathbb{N}_0 \cup \{\infty\}$ mean?

A random variable $X$ takes values in $\mathbb{N}_0 \cup \{\infty\}$? Does it just mean $X$ takes values $0
Gary
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What does $\mathbb{R} \setminus S$ mean?

What does $\mathbb{R}\setminus S$ mean? I am not getting it what it actually means. I have found it manywhere in real-analysis like in the definition of boundary points of a set. Can anyone tell me what it means really?
user142971
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Set Notation help?

If $A=\{a_1,a_2,\dots,a_7\}$ and we want to know how many $3$ element subsets exist in $A$, would we simply use ${7\choose3}=35$ on a calculator, or does this notation not account for the empty set, in which case we would do ${8\choose3}=56$?
Xan Xero
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Strict ceiling and floor notation

The normal ceiling and floor functions, denoted $\lceil x \rceil$ and $\lfloor x \rfloor$ respectively, refer to the smallest integer greater than or equal to $x$, and similar for the floor function. I have a need for some notation to represent the…
Cameron Martin
  • 576
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What does this notation mean? $x \mapsto f(x)$

What does this notation mean? $x \mapsto f(x)$ I've seen it at the beginning of functions but don't know what it is.
YoTengoUnLCD
  • 13,384
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Why is there no symbol for rounding to different precisions?

I was taught in a school that one uses rounding for different precision with just the symbol $\approx$, like $13.46\approx 13.5$ or $13.46\approx 13$ depending on the situation. Why are there no different notations to round to different precision,…
guest
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How to show range in equation for multiple variables?

I'd like to show in the below equation that variables $i$ and $j$ need to be chosen from the range $1$ to $n$, but I am not sure how to properly show this. Can somebody please show me the proper notation for this? $y=f(i,j) \qquad i,j =…
NESHOM
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Does "$\dots$" imply countability?

I am given an arbitrary set $S$. If I say the following: "Suppose that the elements of $S$ are labeled $x_1,x_2,x_3,\dots,$" am I notationally implying that the number of elements in $S$ is countable? This issue came up when I was grading papers…
Peter Woolfitt
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There is a logical or mathematical symbol for compatibility/incompatibility?

Exists a symbol in logic or mathematics to relate two or more compatibility or incompatibility conditions? I dont want to specify a determined area of study (topology, algebra, etc...) I just want to know about this topic in a broad sense, if it…
Masacroso
  • 30,417
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Implementing the $\Rightarrow \Leftarrow$ contradiction symbol?

How is the $\Rightarrow \Leftarrow$ symbol actually used in practice? I think my issue here is that I don't know what the symbol is meant to mean. For example, I know that $\implies$ means "which implies", and $\iff$ means "if and only if" or "iff".…
Is Ne
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Notation for image and kernel capitalization of first letter

In the mathematical notation for image and kernel one usually writes $\ker$ for kernel and $\DeclareMathOperator{\img}{Im}\img$ for image. Why is the "k" small but the "I" big?
Loreno Heer
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How to denote the size of a list?

Suppose I have a list (not a set) with entries $[x, x, x, y, z]$. Then the list is size of $5$. What is the mathematical function that returns the number of elements? Does cardinality only work on sets?
Olórin
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