In the Hanyu Pinyin official romanization system for Chinese, diacritics are used to mark the tones of the syllables in which the marked vowels occur.
In orthography and collation, a letter modified by a diacritic may be treated either as a new, distinct letter or as a letter–diacritic combination.
But the accented vowels á, é, í, ó, ú are not separated from the unaccented vowels a, e, i, o, u, as the acute accent in Spanish only modifies stress within the word or denotes a distinction between homonyms, and does not modify the sound of a letter.
For a comprehensive list of the collating orders in various languages, see Collating sequence.
In abugida scripts, like those used to write Hindi and Thai, diacritics indicate vowels, and may occur above, below, before, after, or around the consonant letter they modify.
The tittle (dot) on the letter i of the Latin alphabet originated as a diacritic to clearly distinguish i from the minims (downstrokes) of adjacent letters.
Efforts have been made to create internationalized domain names that further extend the English alphabet (e.g., "pokémon.com").
Such a key is sometimes referred to as a dead key, as it produces no output of its own but modifies the output of the key pressed after it.
In modern Microsoft Windows and Linux operating systems, the keyboard layouts US International and UK International feature dead keys that allow one to type Latin letters with the acute, grave, circumflex, diæresis, tilde, and cedilla found in Western European languages (specifically, those combinations found in the ISO Latin-1 character set) directly: ¨ e gives ë, ~ o gives õ, etc.
It first appeared in the 11th century in the sequence ii (as in ingeníí), then spread to i adjacent to m, n, u, and finally to all lowercase i's.
The j, originally a variant of i, inherited the tittle.
This varies from language to language, and may vary from case to case within a language.