What ̈ means
Type the base letter first, then this mark.
In äu, the dots belong to a, not u. This character has no spacing width of its own; alone, it may look blank, appear on a dotted circle (a display placeholder), or attach incorrectly, depending on the font or text field.
Why do the same two dots mean different things?
The language around them decides their job.
Diaeresis and umlaut have different jobs: in Greek and French spelling, the trema or diaeresis can keep adjacent vowels in separate syllables; English retains the mark in some names and loanwords. German umlaut uses similar-looking dots to change vowel quality. The word's language tells you which reading applies.
An early Greek manuscript on papyrus, a plant-based writing material, P.Mert. II 83 (175–199 CE), uses the mark to separate vowels and sometimes signal a word or clause boundary in writing without spaces. By the ninth century, Greek minuscule—a small-letter book hand—had word division, reducing the mark's boundary role.
A writing mark, not a message reaction.
Attach it to the intended letter; alone, it may vanish, show a placeholder, or land on the wrong character.
Don't confuse it with
1Questions people ask
2Why does a combining mark show a dotted circle?
The circle is a placeholder, not part of the mark. Unicode charts use it to show where a base would sit; a font or text field may show it when the mark has no suitable base.
Why did my combining mark disappear when pasted?
It is a display limitation. Some fonts and text fields do not render an isolated combining mark; place it after its intended letter, or use the spacing form for dots that must stand alone.
How to type ̈
̈\0308Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.