Languages that treat accented letters as variants of the underlying letter usually alphabetize words with such symbols immediately after similar unmarked words. in phone books or in author catalogues in libraries), umlauts are often treated as combinations of the vowel with a suffixed e; Austrian phone books now treat characters with umlauts as separate letters (immediately following the underlying vowel).
For instance, in German where two words differ only by an umlaut, the word without it is sorted first in German dictionaries (e.g. In Spanish, the grapheme ñ is considered a new letter different from n and collated between n and o, as it denotes a different sound from that of a plain n.
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.
Examples are the diaereses in the borrowed French words naïve and Noël, which show that the vowel with the diaeresis mark is pronounced separately from the preceding vowel; the acute and grave accents, which can indicate that a final vowel is to be pronounced, as in saké and poetic breathèd; and the cedilla under the "c" in the borrowed French word façade, which shows it is pronounced .
French treats letters with diacritical marks the same as the underlying letter for purposes of ordering and dictionaries.
Depending on the keyboard layout, which differs amongst countries, it is more or less easy to enter letters with diacritics on computers and typewriters.
Some have their own keys; some are created by first pressing the key with the diacritic mark followed by the letter to place it on.
In other alphabetic systems, diacritical marks may perform other functions.
Vowel pointing systems, namely the Arabic harakat ( ), which, respectively, mark abbreviations or acronyms, and Greek diacritical marks, which showed that letters of the alphabet were being used as numerals.
The shape of the diacritic developed from initially resembling today's acute accent to a long flourish by the 15th century.