No single sign means concatenation: copy ‖, ⋅ or ⁀, each with the field that writes it.
Math Symbol for Concatenation
‖Double vertical lineU+2016Ready to copy
26 signs and strings. Tap any value to copy it.
26 signs and strings. A character and its name both copy the character. A code copies the code.
Character
Name
Code point
Alt code
Option keys
HTML
LaTeX
U+2016. Two upright bars as one character. Between two values they join them end to end: x ‖ y is y put straight after x, the notation of computer science and cryptography. ‖ in HTML, \Vert in LaTeX.
U+22C5. The concatenation dot of formal language theory: s ⋅ t is the string s followed by the string t. ⋅ in HTML, \cdot in LaTeX.
U+2040. Unicode's other name for it is z notation sequence concatenation: s ⁀ t joins the sequences s and t.
U+29FA. Two plus signs as one character, in Unicode since version 3.2 (2002). Some programming languages type ++ to join two lists.
The digits of 34 put straight after 12, which makes 1234. Put your own two values in place of the numbers.
s, U+22C5, t: the string s followed by the string t.
x, U+2016, y: the same with letters, the digits of y put after the digits of x.
s, U+2040, t: the sequence s with the sequence t after it, as Z notation writes it.
No sign at all: s and t written next to each other is the usual way to show their concatenation.
Every string of the set S followed by every string of the set T.
The tie and a slash before q: in Z notation, every sequence in q joined into one.
a and b with two typed plus signs between them, as some programming languages join lists.
U+2225. The parallel sign of geometry. The same two bars between two values are read as concatenation in computer science. ∥ in HTML, \parallel in LaTeX.
The typed form, the keyboard's vertical line U+007C twice. Standards and scientific papers write concatenation this way, and so do some programming languages.
U+00B7. The midpoint of typography, a look-alike of ⋅ that a keyboard can reach: Alt+250, Alt+0183 or Option+Shift+9. · in HTML.
U+002B. On the keyboard. In some programming languages "a" + "b" is "ab". + in HTML.
The typed form of ⧺: some programming languages join two lists or strings with it.
U+0026. On the keyboard. A spreadsheet formula joins two pieces of text with it. & in HTML.
Written in some texts for joining two tuples, the ordered lists of mathematics.
U+2322. A curve that Unicode cross-refers to the character tie. ⌢ in HTML, \frown in LaTeX.
U+2050. Unicode's note: editing mark. A proofreader uses it to close up a word that a space has split in two.
U+203F. The tie under the line. Proofreaders once marked a word wrongly split by a space with it.
U+03B5. Written for the empty string. Joining it to a string changes nothing: s ⋅ ε is s. Alt+238, ε in HTML, \varepsilon in LaTeX.
Every string that can be made from the letters of the alphabet Σ, the empty string among them.
U+27E8. Opens a sequence. Unicode's other names for it are bra and z notation left sequence bracket. ⟨ in HTML, \langle in LaTeX.
U+27E9. Closes a sequence. Unicode's other names for it are ket and z notation right sequence bracket. ⟩ in HTML, \rangle in LaTeX.
To write concatenation, computer science and cryptography put ‖ between two values, formal language theory a dot or nothing at all, and Z notation the tie ⁀.
Read the full guide
Typing them
No key carries ‖, ⋅, ⁀ or ⧺. A web page writes ‖ and ⋅, and LaTeX \Vert and \cdot. Standards and scientific papers type ‖ as two vertical lines, ||. Alt+250 types ·, the midpoint of typography, a look-alike of ⋅. LaTeX's \frown draws ⌢, the curve Unicode cross-refers to the tie.
The empty string, ε, changes nothing: s ⋅ ε is s.
Order counts: snow joined to ball is snowball, and ball joined to snow is not.
In pairs the bars mean something else: ‖x‖ is a norm.
Questions and answers
What does the concatenation symbol ‖ mean in math?
x ‖ y is the value made by putting y's digits after the end of x. The notation is typical of computer science. In geometry the same two bars say that two lines are parallel.
Is there a dot concatenation symbol in math?
Yes. Formal language theory writes s ⋅ t for the string s followed by the string t, and S ⋅ T for two sets of strings joined the same way. The character is ⋅, the dot operator, U+22C5.
What is the math symbol for ordered set concatenation?
For an ordered set of items, a sequence or a tuple, it is the tie: s ⁀ t in Z notation. Some texts write a double colon. Plain sets have no order to join end to end; they are united with ∪.
Which symbol do you use to concatenate in code?
It depends on the language. Some programming languages join strings with +, some join lists with ++, and some use ||; a spreadsheet formula uses &. ⧺ is the double plus as one character.
All 26 signs and strings
Start here 6
12‖3412 joined to 34The digits of 34 put straight after 12, which makes 1234. Put your own two values in place of the numbers.
⁀Character tieU+2040. Unicode's other name for it is z notation sequence concatenation: s ⁀ t joins the sequences s and t.
⋅Dot operatorU+22C5. The concatenation dot of formal language theory: s ⋅ t is the string s followed by the string t. ⋅ in HTML, \cdot in LaTeX.
⧺Double plusU+29FA. Two plus signs as one character, in Unicode since version 3.2 (2002). Some programming languages type ++ to join two lists.
‖Double vertical lineU+2016. Two upright bars as one character. Between two values they join them end to end: x ‖ y is y put straight after x, the notation of computer science and cryptography. ‖ in HTML, \Vert in LaTeX.
s⋅tTwo strings joined with a dots, U+22C5, t: the string s followed by the string t.
Show all 26 signs and strings (20 more)
Ready to edit 6
⁀/qDistributed concatenationThe tie and a slash before q: in Z notation, every sequence in q joined into one.
a++bTwo lists joined in codea and b with two typed plus signs between them, as some programming languages join lists.
s⁀tTwo sequences joined with a ties, U+2040, t: the sequence s with the sequence t after it, as Z notation writes it.
S⋅TTwo sets of strings joinedEvery string of the set S followed by every string of the set T.
stTwo strings side by sideNo sign at all: s and t written next to each other is the usual way to show their concatenation.
x‖yx joined to yx, U+2016, y: the same with letters, the digits of y put after the digits of x.
Two bars 2
∥Parallel toU+2225. The parallel sign of geometry. The same two bars between two values are read as concatenation in computer science. ∥ in HTML, \parallel in LaTeX.
||Two vertical linesThe typed form, the keyboard's vertical line U+007C twice. Standards and scientific papers write concatenation this way, and so do some programming languages.
Dots 1
·Middle dotU+00B7. The midpoint of typography, a look-alike of ⋅ that a keyboard can reach: Alt+250, Alt+0183 or Option+Shift+9. · in HTML.
Ties 3
⁐Close upU+2050. Unicode's note: editing mark. A proofreader uses it to close up a word that a space has split in two.
⌢FrownU+2322. A curve that Unicode cross-refers to the character tie. ⌢ in HTML, \frown in LaTeX.
‿UndertieU+203F. The tie under the line. Proofreaders once marked a word wrongly split by a space with it.
In code 4
&AmpersandU+0026. On the keyboard. A spreadsheet formula joins two pieces of text with it. & in HTML.
+Plus signU+002B. On the keyboard. In some programming languages "a" + "b" is "ab". + in HTML.
::Two colonsWritten in some texts for joining two tuples, the ordered lists of mathematics.
++Two plus signsThe typed form of ⧺: some programming languages join two lists or strings with it.
Written with them 4
εGreek small letter epsilonU+03B5. Written for the empty string. Joining it to a string changes nothing: s ⋅ ε is s. Alt+238, ε in HTML, \varepsilon in LaTeX.
⟨Mathematical left angle bracketU+27E8. Opens a sequence. Unicode's other names for it are bra and z notation left sequence bracket. ⟨ in HTML, \langle in LaTeX.
⟩Mathematical right angle bracketU+27E9. Closes a sequence. Unicode's other names for it are ket and z notation right sequence bracket. ⟩ in HTML, \rangle in LaTeX.
Σ*Sigma starEvery string that can be made from the letters of the alphabet Σ, the empty string among them.