Source: Noto Sans

U+0308 Combining Diaeresis

U+0308 was added in Unicode version 1.1 in 1993. It belongs to the block U+0300 to U+036F Combining Diacritical Marks in the U+0000 to U+FFFF Basic Multilingual Plane.

This character is a Nonspacing Mark and inherits its script property from the preceding character. It is also used in the scripts Armenian, Cyrillic, Duployan shorthand, Gothic, Greek, Hebrew, Latin, Old Permic, Syriac, Tai Le. The character is also known as double dot above, umlaut, Greek dialytika and double derivative.

The glyph is not a composition. Its width in East Asian texts is determined by its context. It can be displayed wide or narrow. In bidirectional text it acts as Nonspacing Mark. When changing direction it is not mirrored. U+0308 prohibits a line break before it. The glyph can be confused with 8 other glyphs.

The Wikipedia has the following information about this codepoint:

Diacritical marks of two dots ¨, placed side-by-side over or under a letter, are used in several languages for several different purposes. The most familiar to English-language speakers are the diaeresis and the umlaut, though there are numerous others. For example, in Albanian, ë represents a schwa. Such diacritics are also sometimes used for stylistic reasons (as in the family name Brontë or the band name Mötley Crüe).
In modern computer systems using Unicode, the two-dot diacritics are almost always encoded identically, having the same code point. For example, U+00F6 ö LATIN SMALL LETTER O WITH DIAERESIS represents both o-umlaut and o-diaeresis. Their appearance in print or on screen may vary between typefaces but rarely within the same typeface.
The word trema (French: tréma), used in linguistics and also classical scholarship, describes the form of both the umlaut diacritic and the diaeresis rather than their function and is used in those contexts to refer to either.

Representations

System	Representation (click value to copy)
Nº	776
UTF-8	CC 88
UTF-16	03 08
UTF-32	00 00 03 08
URL-Quoted	%CC%88
HTML hex reference	̈
Wrong windows-1252 Mojibake	â—ŒÌˆ
alias	double dot above
alias	umlaut
alias	Greek dialytika
alias	double derivative
Encoding: EUC_JIS_2004 (hex bytes)	AB ED
Encoding: EUC_JISX0213 (hex bytes)	AB ED
Encoding: GB18030 (hex bytes)	81 30 BD 34
Encoding: ISO2022_JP_2004 (hex bytes)	1B 24 28 51 2B 6D 1B 28 42
Encoding: ISO2022_JP_3 (hex bytes)	1B 24 28 4F 2B 6D 1B 28 42
Encoding: SHIFT_JIS_2004 (hex bytes)	86 8D
Encoding: SHIFT_JISX0213 (hex bytes)	86 8D
LATEX	\"
AGL: Latin-4	uni0308
AGL: Latin-5	uni0308
Adobe Glyph List	dieresiscmb
RFC 5137	\u'0308'
Bash and Zsh inside `echo -e`	\u0308
C and C++	\u0308
C#	\u0308
CSS	\000308
Excel	=UNICHAR(776)
Go	\u0308
JavaScript	\u0308
Modern JavaScript since ES6	\u{308}
JSON	\u0308
Java	\u0308
Lua	\u{308}
Matlab	char(776)
Perl	"\x{308}"
PHP	\u{308}
PostgreSQL	U&'\0308'
PowerShell	`u{308}
Python	\u0308
Ruby	\u{308}
Rust	\u{308}
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Related Characters

Confusables

Arabic Tone Two Dots Above

NKo Combining Double Dot Above

Hyphen with Diaeresis

Apl Functional Symbol Jot Diaeresis

Apl Functional Symbol Del Diaeresis

Apl Functional Symbol Tilde Diaeresis

Apl Functional Symbol Star Diaeresis

Apl Functional Symbol Up Tack Diaeresis

Elsewhere

Complete Record

Property	Value
Age (age)	1.1 (1993)
Unicode Name (na)	COMBINING DIAERESIS
Unicode 1 Name (na1)	NON-SPACING DIAERESIS
Block (blk)	Combining Diacritical Marks
General Category (gc)	Nonspacing Mark
Script (sc)	Inherited
Bidirectional Category (bc)	Nonspacing Mark
Combining Class (ccc)	Above
Decomposition Type (dt)	none
Decomposition Mapping (dm)	Combining Diaeresis
Lowercase (Lower)	✘
Simple Lowercase Mapping (slc)	Combining Diaeresis
Lowercase Mapping (lc)	Combining Diaeresis
Uppercase (Upper)	✘
Simple Uppercase Mapping (suc)	Combining Diaeresis
Uppercase Mapping (uc)	Combining Diaeresis
Simple Titlecase Mapping (stc)	Combining Diaeresis
Titlecase Mapping (tc)	Combining Diaeresis
Case Folding (cf)	Combining Diaeresis
ASCII Hex Digit (AHex)	✘
Alphabetic (Alpha)	✘
Bidi Control (Bidi_C)	✘
Bidi Mirrored (Bidi_M)	✘
Composition Exclusion (CE)	✘
Case Ignorable (CI)	✔
Changes When Casefolded (CWCF)	✘
Changes When Casemapped (CWCM)	✘
Changes When NFKC Casefolded (CWKCF)	✘
Changes When Lowercased (CWL)	✘
Changes When Titlecased (CWT)	✘
Changes When Uppercased (CWU)	✘
Cased (Cased)	✘
Full Composition Exclusion (Comp_Ex)	✘
Default Ignorable Code Point (DI)	✘
Dash (Dash)	✘
Deprecated (Dep)	✘
Diacritic (Dia)	✔
Emoji Modifier Base (EBase)	✘
Emoji Component (EComp)	✘
Emoji Modifier (EMod)	✘
Emoji Presentation (EPres)	✘
Emoji (Emoji)	✘
Extender (Ext)	✘
Extended Pictographic (ExtPict)	✘
FC NFKC Closure (FC_NFKC)	Combining Diaeresis
Grapheme Cluster Break (GCB)	Extend
Grapheme Base (Gr_Base)	✘
Grapheme Extend (Gr_Ext)	✔
Grapheme Link (Gr_Link)	✘
Hex Digit (Hex)	✘
Hyphen (Hyphen)	✘
ID Continue (IDC)	✔
ID Start (IDS)	✘
IDS Binary Operator (IDSB)	✘
IDS Trinary Operator and (IDST)	✘
IDSU (IDSU)	0
ID_Compat_Math_Continue (ID_Compat_Math_Continue)	0
ID_Compat_Math_Start (ID_Compat_Math_Start)	0
Ideographic (Ideo)	✘
InCB (InCB)	Extend
Indic Mantra Category (InMC)	—
Indic Positional Category (InPC)	NA
Indic Syllabic Category (InSC)	Other
Jamo Short Name (JSN)	—
Join Control (Join_C)	✘
Logical Order Exception (LOE)	✘
Modifier Combining Mark (MCM)	✘
Math (Math)	✘
Noncharacter Code Point (NChar)	✘
NFC Quick Check (NFC_QC)	Maybe
NFD Quick Check (NFD_QC)	Yes
NFKC Casefold (NFKC_CF)	Combining Diaeresis
NFKC Quick Check (NFKC_QC)	Maybe
NFKC_SCF (NFKC_SCF)	Combining Diaeresis
NFKD Quick Check (NFKD_QC)	Yes
Other Alphabetic (OAlpha)	✘
Other Default Ignorable Code Point (ODI)	✘
Other Grapheme Extend (OGr_Ext)	✘
Other ID Continue (OIDC)	✘
Other ID Start (OIDS)	✘
Other Lowercase (OLower)	✘
Other Math (OMath)	✘
Other Uppercase (OUpper)	✘
Prepended Concatenation Mark (PCM)	✘
Pattern Syntax (Pat_Syn)	✘
Pattern White Space (Pat_WS)	✘
Quotation Mark (QMark)	✘
Regional Indicator (RI)	✘
Radical (Radical)	✘
Sentence Break (SB)	Extend
Soft Dotted (SD)	✘
Sentence Terminal (STerm)	✘
Terminal Punctuation (Term)	✘
Unified Ideograph (UIdeo)	✘
Variation Selector (VS)	✘
Word Break (WB)	Extend
White Space (WSpace)	✘
XID Continue (XIDC)	✔
XID Start (XIDS)	✘
Expands On NFC (XO_NFC)	✘
Expands On NFD (XO_NFD)	✘
Expands On NFKC (XO_NFKC)	✘
Expands On NFKD (XO_NFKD)	✘
Bidi Paired Bracket (bpb)	Combining Diaeresis
Bidi Paired Bracket Type (bpt)	None
East Asian Width (ea)	ambiguous
Hangul Syllable Type (hst)	Not Applicable
ISO 10646 Comment (isc)	—
Joining Group (jg)	No_Joining_Group
Joining Type (jt)	Transparent
Line Break (lb)	Combining Mark
Numeric Type (nt)	none
Numeric Value (nv)	not a number
Simple Case Folding (scf)	Combining Diaeresis
Script Extension (scx)	Armenian Cyrillic Duployan shorthand Gothic Greek Hebrew Latin Old Permic Syriac Tai Le
Vertical Orientation (vo)	R