<s>
In	O
SGML	B-Language
,	O
HTML	B-Language
and	O
XML	B-Protocol
documents	I-Protocol
,	O
the	O
logical	O
constructs	O
known	O
as	O
character	O
data	O
and	O
attribute	O
values	O
consist	O
of	O
sequences	O
of	O
characters	O
,	O
in	O
which	O
each	O
character	O
can	O
manifest	O
directly	O
(	O
representing	O
itself	O
)	O
,	O
or	O
can	O
be	O
represented	O
by	O
a	O
series	O
of	O
characters	O
called	O
a	O
character	O
reference	O
,	O
of	O
which	O
there	O
are	O
two	O
types	O
:	O
a	O
numeric	B-General_Concept
character	I-General_Concept
reference	I-General_Concept
and	O
a	O
character	B-General_Concept
entity	I-General_Concept
reference	I-General_Concept
.	O
</s>
<s>
This	O
article	O
lists	O
the	O
character	B-General_Concept
entity	I-General_Concept
references	I-General_Concept
that	O
are	O
valid	O
in	O
HTML	B-Language
and	O
XML	B-Protocol
documents	I-Protocol
.	O
</s>
<s>
A	O
character	B-General_Concept
entity	I-General_Concept
reference	I-General_Concept
refers	O
to	O
the	O
content	O
of	O
a	O
named	O
entity	B-Language
.	O
</s>
<s>
An	O
entity	B-Language
declaration	O
is	O
created	O
by	O
using	O
the	O
<!ENTITY name "value">	O
syntax	O
in	O
a	O
Document	B-Language
type	I-Language
definition	I-Language
(	O
DTD	B-Language
)	O
.	O
</s>
<s>
A	O
numeric	B-General_Concept
character	I-General_Concept
reference	I-General_Concept
refers	O
to	O
a	O
character	O
by	O
its	O
Universal	O
Character	O
Set/Unicode	O
code	O
point	O
,	O
and	O
uses	O
the	O
format	O
:	O
</s>
<s>
where	O
nnnn	O
is	O
the	O
code	O
point	O
in	O
decimal	B-Application
form	O
,	O
and	O
hhhh	O
is	O
the	O
code	O
point	O
in	O
hexadecimal	O
form	O
.	O
</s>
<s>
The	O
x	O
must	O
be	O
lowercase	O
in	O
XML	B-Protocol
documents	I-Protocol
.	O
</s>
<s>
In	O
contrast	O
,	O
a	O
character	B-General_Concept
entity	I-General_Concept
reference	I-General_Concept
refers	O
to	O
a	O
character	O
by	O
the	O
name	O
of	O
an	O
entity	B-Language
which	O
has	O
the	O
desired	O
character	O
as	O
its	O
replacement	O
text	O
.	O
</s>
<s>
The	O
entity	B-Language
must	O
either	O
be	O
predefined	O
(	O
built	O
into	O
the	O
markup	O
language	O
)	O
or	O
explicitly	O
declared	O
in	O
a	O
Document	B-Language
Type	I-Language
Definition	I-Language
(	O
DTD	B-Language
)	O
.	O
</s>
<s>
The	O
format	O
is	O
the	O
same	O
as	O
for	O
any	O
entity	B-Language
reference	O
:	O
</s>
<s>
where	O
name	O
is	O
the	O
case-sensitive	O
name	O
of	O
the	O
entity	B-Language
.	O
</s>
<s>
ISO	O
Entity	B-Language
Sets	O
SGML	B-Language
supplied	O
a	O
comprehensive	O
set	O
of	O
entity	B-Language
declarations	O
for	O
characters	O
widely	O
used	O
in	O
Western	O
technical	O
and	O
reference	O
publishing	O
,	O
for	O
Latin	O
,	O
Greek	O
and	O
Cyrillic	O
scripts	O
.	O
</s>
<s>
HTML	B-General_Concept
Entity	I-General_Concept
Sets	O
Early	O
versions	O
of	O
HTML	B-Language
built	O
in	O
small	O
subsets	O
of	O
these	O
,	O
relating	O
to	O
characters	O
found	O
in	O
three	O
Western	O
8-bit	O
fonts	O
.	O
</s>
<s>
MathML	B-Language
Entity	B-Language
Sets	O
The	O
W3C	O
developed	O
a	O
set	O
of	O
entity	B-Language
declarations	O
for	O
MathML	B-Language
characters	O
.	O
</s>
<s>
XML	B-Language
Entity	I-Language
Sets	O
The	O
W3C	O
MathML	B-Language
Working	O
Group	O
took	O
over	O
maintenance	O
of	O
the	O
ISO	O
public	O
entity	B-Language
sets	O
,	O
combined	O
with	O
the	O
MathML	B-Language
and	O
documents	O
them	O
in	O
.	O
</s>
<s>
This	O
set	O
can	O
support	O
the	O
requirements	O
of	O
XHTML	B-Language
,	O
MathML	B-Language
and	O
as	O
an	O
input	O
to	O
future	O
versions	O
of	O
HTML	B-Language
.	O
</s>
<s>
HTML	B-Application
5	I-Application
HTML5	B-Application
adopts	O
the	O
XML	B-Language
entities	I-Language
as	O
,	O
however	O
it	O
restates	O
them	O
without	O
reference	O
to	O
their	O
sources	O
and	O
does	O
not	O
group	O
them	O
into	O
sets	O
.	O
</s>
<s>
The	O
HTML	B-Application
5	I-Application
specification	O
additionally	O
provides	O
mappings	O
from	O
the	O
names	O
to	O
Unicode	O
character	O
sequences	O
using	O
JSON	B-General_Concept
.	O
</s>
<s>
Numerous	O
other	O
entity	B-Language
sets	O
have	O
been	O
developed	O
for	O
special	O
requirements	O
,	O
and	O
for	O
major	O
and	O
minority	O
scripts	O
.	O
</s>
<s>
The	O
XML	B-Protocol
specification	I-Protocol
does	O
not	O
use	O
the	O
term	O
"	O
character	B-General_Concept
entity	I-General_Concept
"	O
or	O
"	O
character	B-General_Concept
entity	I-General_Concept
reference	I-General_Concept
"	O
.	O
</s>
<s>
The	O
XML	B-Protocol
specification	I-Protocol
defines	O
five	O
"	O
predefined	O
entities	O
"	O
representing	O
special	O
characters	O
,	O
and	O
requires	O
that	O
all	O
XML	B-Protocol
processors	O
honor	O
them	O
.	O
</s>
<s>
The	O
entities	O
can	O
be	O
explicitly	O
declared	O
in	O
a	O
DTD	B-Language
,	O
as	O
well	O
,	O
but	O
if	O
this	O
is	O
done	O
,	O
the	O
replacement	O
text	O
must	O
be	O
the	O
same	O
as	O
the	O
built-in	O
definitions	O
.	O
</s>
<s>
XML	B-Protocol
also	O
allows	O
other	O
named	O
entities	O
of	O
any	O
size	O
to	O
be	O
defined	O
on	O
a	O
per-document	O
basis	O
.	O
</s>
<s>
The	O
table	O
below	O
lists	O
the	O
five	O
XML	B-Protocol
predefined	O
entities	O
.	O
</s>
<s>
The	O
initial	O
"	O
Name	O
"	O
column	O
mentions	O
the	O
entity	B-Language
's	O
name	O
.	O
</s>
<s>
The	O
decimal	B-Application
equivalent	O
of	O
the	O
code	O
point	O
is	O
then	O
shown	O
in	O
parentheses	O
.	O
</s>
<s>
The	O
"	O
Standard	O
"	O
column	O
indicates	O
the	O
first	O
version	O
of	O
XML	B-Protocol
that	O
includes	O
the	O
entity	B-Language
.	O
</s>
<s>
The	O
HTML	B-Application
5	I-Application
DTDs	O
define	O
many	O
named	O
entities	O
,	O
references	O
to	O
which	O
act	O
as	O
mnemonic	O
aliases	O
for	O
certain	O
Unicode	O
characters	O
.	O
</s>
<s>
The	O
HTML	B-Application
5	I-Application
specification	O
requires	O
the	O
use	O
of	O
the	O
standard	O
DTDs	O
and	O
does	O
not	O
allow	O
users	O
to	O
define	O
additional	O
entities	O
.	O
</s>
<s>
In	O
the	O
table	O
below	O
,	O
the	O
"	O
Standard	O
"	O
column	O
indicates	O
the	O
first	O
version	O
of	O
the	O
HTML	B-Language
DTD	B-Language
that	O
defines	O
the	O
character	B-General_Concept
entity	I-General_Concept
reference	I-General_Concept
.	O
</s>
<s>
To	O
use	O
one	O
of	O
these	O
character	B-General_Concept
entity	I-General_Concept
references	I-General_Concept
in	O
an	O
HTML	B-Language
or	O
XML	B-Protocol
document	I-Protocol
,	O
enter	O
an	O
ampersand	O
followed	O
by	O
the	O
entity	B-Language
name	O
and	O
a	O
semicolon	O
,	O
e.g.	O
,	O
enter	O
©	O
for	O
the	O
copyright	O
symbol	O
.	O
</s>
<s>
Entities	O
codepoint	O
Standard	O
DTD	B-Language
Old	O
ISO	O
subset	O
Description	O
U+0009	O
HTML	B-Application
5.0	I-Application
character	O
tabulation	O
U+000A	O
HTML	B-Application
5.0	I-Application
line	O
feed	O
(	O
LF	O
)	O
!	B-Device
</s>
<s>
U+0021	O
HTML	B-Application
5.0	I-Application
ISOnum	O
exclamation	O
mark	O
"	O
U+0022	O
HTMLspecial	O
ISOnum	O
quotation	O
mark	O
#	O
U+0023	O
HTML	B-Application
5.0	I-Application
number	O
sign	O
$	O
U+0024	O
HTML	B-Application
5.0	I-Application
dollar	O
sign	O
%	O
U+0025	O
HTML	B-Application
5.0	I-Application
ISOnum	O
percent	O
sign	O
&	O
U+0026	O
html.dtdHTMLspecial	O
ISOnum	O
ampersand	O
'	O
U+0027	O
HTML	B-Language
5.0Also	O
XHTML	B-Language
1.0	I-Language
HTMLspecial	O
ISOnum	O
apostrophe	B-Language
(	O
apostrophe-quote	O
)	O
;	B-Device
see	O
below	O
(	O
U+0028	O
HTML	B-Application
5.0	I-Application
left	O
parenthesis	O
)	O
U+0029	O
HTML	B-Application
5.0	I-Application
right	O
parenthesis	O
*	B-Device
U+002A	O
HTML	B-Application
5.0	I-Application
asterisk	B-Language
(	O
middle	O
asterisk	B-Language
)	O
+	O
U+002B	O
HTML	B-Application
5.0	I-Application
plus	O
sign	O
,	O
U+002C	O
HTML	B-Application
5.0	I-Application
comma	O
.	O
</s>
<s>
U+002E	O
HTML	B-Application
5.0	I-Application
full	O
stop	O
(	O
period	O
)	O
/	O
U+002F	O
HTML	B-Application
5.0	I-Application
solidus	O
:	O
U+003A	O
HTML	B-Application
5.0	I-Application
colon	O
;	B-Device
U+003B	O
HTML	B-Application
5.0	I-Application
semicolon	O
< U+003C  html.dtdHTMLspecial ISOnum less-than sign  = U+003D HTML 5.0  ISOnum equals sign  >	O
U+003E	O
html.dtdHTMLspecial	O
ISOnum	O
greater-than	O
sign	O
?	B-Device
</s>
<s>
The	O
XHTML	B-Language
DTDs	O
explicitly	O
declare	O
253	O
entities	O
(	O
including	O
the	O
5	O
predefined	O
entities	O
of	O
XML	B-Protocol
1.0	O
)	O
whose	O
expansion	O
is	O
a	O
single	O
character	O
,	O
which	O
can	O
therefore	O
be	O
informally	O
referred	O
to	O
as	O
"	O
character	B-General_Concept
entities	I-General_Concept
"	O
.	O
</s>
<s>
These	O
(	O
with	O
the	O
exception	O
of	O
the	O
'	O
entity	B-Language
)	O
have	O
the	O
same	O
names	O
and	O
represent	O
the	O
same	O
characters	O
as	O
the	O
252	O
character	B-General_Concept
entities	I-General_Concept
in	O
HTML	B-Language
.	O
</s>
<s>
Also	O
,	O
by	O
virtue	O
of	O
being	O
XML	B-Protocol
,	O
XHTML	B-Language
documents	O
may	O
reference	O
the	O
predefined	O
'	O
entity	B-Language
,	O
which	O
is	O
not	O
one	O
of	O
the	O
252	O
character	B-General_Concept
entities	I-General_Concept
in	O
HTML	B-Language
4	O
.	O
</s>
<s>
However	O
,	O
the	O
usability	O
of	O
entity	B-Language
references	O
in	O
XHTML	B-Language
is	O
affected	O
by	O
how	O
the	O
document	O
is	O
being	O
processed	O
:	O
</s>
<s>
If	O
the	O
document	O
is	O
read	O
by	O
a	O
conforming	O
HTML	B-Language
processor	O
,	O
then	O
only	O
the	O
252	O
HTML	B-General_Concept
character	I-General_Concept
entities	I-General_Concept
can	O
safely	O
be	O
used	O
.	O
</s>
<s>
The	O
use	O
of	O
'	O
or	O
custom	O
entity	B-Language
references	O
may	O
not	O
be	O
supported	O
and	O
may	O
produce	O
unpredictable	O
results	O
.	O
</s>
<s>
If	O
the	O
document	O
is	O
read	O
by	O
an	O
XML	B-Protocol
parser	I-Protocol
that	O
does	O
not	O
or	O
cannot	O
read	O
external	O
entities	O
,	O
then	O
only	O
the	O
five	O
built-in	O
XML	B-Protocol
character	B-General_Concept
entities	I-General_Concept
(	O
see	O
above	O
)	O
can	O
safely	O
be	O
used	O
,	O
although	O
other	O
entities	O
may	O
be	O
used	O
if	O
they	O
are	O
declared	O
in	O
the	O
internal	O
DTD	B-Language
subset	O
.	O
</s>
<s>
If	O
the	O
document	O
is	O
read	O
by	O
an	O
XML	B-Protocol
parser	I-Protocol
that	O
does	O
read	O
external	O
entities	O
,	O
then	O
the	O
five	O
built-in	O
XML	B-Protocol
character	B-General_Concept
entities	I-General_Concept
can	O
safely	O
be	O
used	O
.	O
</s>
<s>
The	O
other	O
248	O
HTML	B-General_Concept
character	I-General_Concept
entities	I-General_Concept
can	O
be	O
used	O
as	O
long	O
as	O
the	O
XHTML	B-Language
DTD	B-Language
is	O
accessible	O
to	O
the	O
parser	B-Language
at	O
the	O
time	O
the	O
document	O
is	O
read	O
.	O
</s>
<s>
Other	O
entities	O
may	O
also	O
be	O
used	O
if	O
they	O
are	O
declared	O
in	O
the	O
internal	O
DTD	B-Language
subset	O
.	O
</s>
<s>
Because	O
of	O
the	O
special	O
'	O
case	O
mentioned	O
above	O
,	O
only	O
"	O
,	O
&	O
,	O
<	O
,	O
and	O
>	O
will	O
work	O
in	O
all	O
XHTML	B-Language
processing	O
situations	O
.	O
</s>
