Wikipedia
en.wikipedia.org › wiki › Null_sign
Null sign - Wikipedia
8 hours ago - The null sign (∅) is a symbol often used in mathematics for denoting the empty set. The same letter in linguistics represents zero, the lack of an element. It is commonly used in phonology, morphology, and syntax. The symbol ∅ is available at Unicode point U+2205.
Top answer 1 of 2
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According to Wikipedia André Weil (and maybe others) introduced the symbol 
for the empty set. They were inspired by the letter Ø in the Norwegian and Danish alphabet. So, I guess you could argue that the symbol should be pronounced as it is pronounced in these alphabets.
In my experience most mathematicians just call the symbol "empty set".
Note also, that the Wikipedia article says that the symbol is not to be confused with the Greek letter 
or 
.
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Although not mathematics, I thought I would add that in the APL programming language the empty vector is represented by the symbol ⍬, which is pronounced "zilde".
Videos
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What is the Power Set of the Empty Set? | Set Theory - YouTube
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How to type Empty Set symbol in Word - YouTube
Wikipedia
en.wikipedia.org › wiki › Empty_set
Empty set - Wikipedia
February 4, 2026 - Common notations for the empty set include "{ }", " ... {\displaystyle \emptyset } ", and "∅". The latter two symbols were introduced by the Bourbaki group (specifically André Weil) in 1939, inspired by the letter Ø (U+00D8 Ø LATIN CAPITAL LETTER O WITH STROKE) in the Danish and Norwegian ...
Wumbo
wumbo.net › symbols › empty-set
Empty Set Symbol (∅)
The 0 (zero) symbol is used in math to represent the number zero or nothing. ... An empty set, also called the null set, is respresented as a zero with a diagonal line through it or as an empty pair of curly braces.
Reddit
reddit.com › r/mathematics › what letter is the empty set symbol ∅ to you?
r/mathematics on Reddit: What letter is the empty set symbol ∅ to you?
April 7, 2024 - So, the empty set symbol ∅ its own thing, it's not phi, it's not a slashed O... it's an empty set symbol.
Piliapp
piliapp.com › symbols › null-sign
∅ Null Sign
It is unique in that it is a subset of every set, including itself. Windows: Hold down the Alt key and type 8709 on the numeric keypad, then release the Alt key. Mac: Press Option + 0. Linux: Press Ctrl + Shift + u, then type 2205 and press Enter. HTML: Use the named entity ∅ or the numeric ...
Quora
quora.com › What-is-the-name-of-the-symbol-Which-we-use-for-empty-set-in-mathematics
What is the name of the symbol ∅ ? Which we use for empty set in mathematics. - Quora
The symbol ∅ is called the empty set symbol. Its standard names and variants: Empty set (most common English name). Null set (used in some texts; “null” here ≠ null in programming).
CK-12 Foundation
ck12.org › all subjects › cbse math › sets and its types › what is a null set in maths?
What is a null set in maths? - Symbol & Definition | CK-12 Foundation
September 11, 2025 - In mathematics, a null set, also known as an empty set, is a set that contains no elements. It is denoted by the symbol @$\begin{align*}\emptyset\end{align*}@$ or @$\begin{align*}\{\}\end{align*}@$. For example, the set of all integers that are both even and odd is a null set, because no integer ...
Cuemath
cuemath.com › algebra › empty-set
Empty Set - Definitions, Properties, Examples | Null Set
A set that does not contain any element is called an empty set or a null set. An empty set is denoted using the symbol '∅'. It is read as 'phi'. Example: Set X = {}. It is also called a void set or null set.
Quora
quora.com › What-is-the-name-of-the-symbol-used-for-expressing-empty-sets
What is the name of the symbol used for expressing empty sets? - Quora
Answer: It’s called the “empty set symbol.” I wish I could give you some cool name like “octothorpe”, but it was based on the letter Ø from Danish, where it is a Close-mid front rounded vowel and “the name of this letter is the ...
Reddit
reddit.com › r/learnmath › do ∅ and φ both mean null set in set theory?
r/learnmath on Reddit: Do ∅ and Φ both mean null set in set theory?
April 22, 2023 -
My professor's slides use both, and I'm confused if they mean different things. In high school, we used the second representation of phi. Assuming the first one is also phi. I think.
Top answer 1 of 11
91
If both are being used in the context of the empty set then it could just be notational sloppiness from your professor.
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Generally speaking, the first is the empty set and the second is phi, whatever that means in context. Often, when typesetting functionality is limited, phi is used to refer to the empty set — since using the conventional symbol might be very difficult or impossible.
Encyclopedia Britannica
britannica.com › science › null-set
Null set | mathematics | Britannica
A second set could be defined as ... letting them be the two…Read More ... The empty (or void, or null) set, symbolized by {} or Ø, contains no elements at all....
CK-12 Foundation
ck12.org › all subjects › cbse math › sets and its types › what symbol denotes an empty or null set?
What symbol denotes an empty or null set? - Examples, Symbol, & Definition | CK-12 Foundation
September 11, 2025 - In mathematics, an empty set, also known as a null set, is a set that contains no elements. It is denoted by the symbol @$\begin{align*}\emptyset\end{align*}@$ or by @$\begin{align*}\{\}\end{align*}@$. For example, the set of all integers that are both even and odd is an empty set, because ...
Study.com
study.com › math courses › precalculus: high school
Empty Set | Definition & Symbol - Lesson | Study.com
September 1, 2015 - All of these empty set symbols represent the empty set. Moreover, sometimes the empty set is called the null set. However, the null set is a distinction made in measure theory to indicate a set of measure zero.
GeeksforGeeks
geeksforgeeks.org › mathematics › empty-set
Empty Set(Null Set): Definition, Notation, Properties, & Examples - GeeksforGeeks
October 29, 2025 - The empty set, null set, or void set is a set that does not include any elements. The symbol (phi) Φ represents the empty set and is written as Φ = { }.
BYJUS
byjus.com › maths › empty-set
Empty Set
As we know, the outcomes of rolling a die are 1, 2, 3, 4, 5, and 6. Thus, the set with numbers greater than 6 here will be { }. That means there will be no elements and is called the empty set.
Published May 18, 2022 Views 31K
Unicode Compart
compart.com › en › unicode › U+2205
“∅” U+2205 Empty Set Unicode Character
U+2205 is the unicode hex value of the character Empty Set. Char U+2205, Encodings, HTML Entitys:∅,∅,∅, UTF-8 (hex), UTF-16 (hex), UTF-32 (hex)
Teachoo
teachoo.com › 7018 › 1341 › Empty-or-Null-set › category › Null-Set
Empty or Null set - Symbol, Definition and Questions - Teachoo
If number of elements in set is 0, it is an empty set.It is also called null set or void set.Example:A = {x: x is a natural number less than 1}Since, natural number = 1, 2, 3, 4, …There is no natural number less than 1Hence,A = {}or A is an ...
Physics Read
physicsread.com › home › how to write an empty(or null) set symbol(∅) in latex?
How to Write an Empty(or Null) Set Symbol(∅) in LaTeX?
September 24, 2025 - An empty set, also known as a null set, is a unique set that contains no elements. Mathematically, it is represented by either the phi symbol (∅) or curly brackets {}.