What is a diacritic in simple terms?

A diacritic is a small mark added to a letter that changes how the letter is pronounced or what the word means. The acute in café and the tilde in año are both diacritics.

Is a diacritic the same as an accent mark?

In everyday English they are used interchangeably. Strictly, accent marks are the subset that mark stress or pitch, such as the acute and the grave, while diacritic covers every mark including the cedilla, ogonek and caron.

Does English use diacritics?

Rarely, and mostly in borrowed words: café, naïve, résumé, façade, Brontë. English is unusual among European languages in having no diacritic of its own.

Why does the same letter sometimes count as one character and sometimes two?

Unicode allows both. é can be the single code point U+00E9 or the letter e followed by a combining acute accent. They look identical but compare as different strings unless the text is normalised.

Is ñ a letter or an n with a diacritic?

In Spanish it is a separate letter of the alphabet with its own dictionary position between n and o. Technically the tilde is a diacritic, but Spanish treats the result as an independent letter.

What is a diacritic? Accent marks explained

A diacritic is a mark added to a letter that changes how that letter sounds, or which word you are looking at. The acute in café, the tilde in año, the cedilla in garçon and the little hook under Polish ę are all diacritics. English gets by almost entirely without them, which is why English speakers tend to treat them as decoration. In most languages they are load bearing.

The word comes from Greek and means “distinguishing”. That is exactly the job: é is distinguished from e the way b is distinguished from d.

Marks that sit above the letter

Mark	Name	Example letters	Used by
◌́	Acute	á é í ó ú ć ń ś ź	Spanish, French, Portuguese, Polish, Czech, Hungarian, Irish
◌̀	Grave	à è ì ò ù	French, Italian, Catalan, Scottish Gaelic
◌̂	Circumflex	â ê î ô û ŵ ŷ	French, Portuguese, Romanian, Welsh, Esperanto
◌̃	Tilde	ñ ã õ	Spanish, Portuguese, Estonian, Guaraní
◌̈	Diaeresis or umlaut	ä ö ü ë ï ÿ	German, Swedish, Finnish, Turkish, French, Dutch
◌̌	Caron or háček	č š ž ě ř ď ť ň	Czech, Slovak, Croatian, Slovene, Latvian, Lithuanian
◌̆	Breve	ă ğ ŭ	Romanian, Turkish, Vietnamese, Esperanto
◌̄	Macron	ā ē ī ō ū	Latvian, Lithuanian, Māori, Hawaiian, Latin teaching
◌̇	Dot above	ż ė ċ ġ İ	Polish, Lithuanian, Maltese, Turkish, Old Irish
◌̋	Double acute	ő ű	Hungarian only

The double acute is the most language-specific mark in the Latin script: outside Hungarian you will essentially never meet ő or ű.

Marks below, through and around the letter

Mark	Name	Example letters	Used by
◌̧	Cedilla	ç ş	French, Portuguese, Catalan, Turkish, Albanian
◌̦	Comma below	ș ț	Romanian and Moldovan
◌̨	Ogonek	ą ę į ų	Polish, Lithuanian, Navajo
◌̊	Ring above	å ů	Danish, Norwegian, Swedish, Czech
◌̸	Stroke or slash	ø ł đ ħ ŧ	Danish, Norwegian, Polish, Croatian, Maltese
◌̣	Dot below	ạ ẹ ị ọ ụ ṣ	Vietnamese, Yoruba, Sanskrit transliteration
◌̛	Horn	ơ ư	Vietnamese only
◌̉	Hook above	ả ẻ ỉ ỏ ủ	Vietnamese only

Two of these are often miscalled. The Romanian comma below in ș is not a cedilla, even though careless fonts and old keyboards produced the cedilla forms ş and ţ for decades. And the ogonek under Polish ą hooks to the right under a vowel, while the cedilla hooks to the left under a consonant.

When the mark makes a whole new letter

Here is the distinction most guides skip. In some languages an accented vowel is still the same letter, just marked. In others the marked form is an independent letter with its own place in the alphabet and its own dictionary entry.

Spanish: á é í ó ú are still a, e, i, o, u. But ñ is a separate letter, sorted between n and o.
Swedish: å ä ö are three separate letters, sorted after z, in that order. They are not “a with dots”.
Czech: č, š, ž and ř are separate letters; the long vowels á é í ó ú ý are not.
Polish: all nine of ą ć ę ł ń ó ś ź ż are separate letters, each sorted immediately after its base.
Turkish: ı and i are two different letters, with two different capitals, I and İ.
German: ä ö ü are not separate alphabet letters, and ß behaves as a variant of ss.

This is why “just drop the accent” is bad advice. Dropping the mark from a Swedish ö changes the letter, not the spelling.

One character or two? Precomposed and combining

Unicode offers two ways to build the same visible letter.

A precomposed letter is a single code point: é is U+00E9, ñ is U+00F1, ǫ is one character. A combining sequence is the plain letter followed by a combining mark: e (U+0065) plus the combining acute accent (U+0301). There are 112 combining marks in the main Unicode block, enough to stack a mark on almost anything.

On screen these two forms are identical. In software they are not. "é" === "é" is false in JavaScript if one side is precomposed and the other is combining, a search for “resume” misses “résumé”, and the same filename can appear twice. The fix is normalisation: NFC composes everything into single code points, NFD decomposes everything into base plus marks. Store and serve NFC, which is what the web expects and what most keyboards produce.

Vietnamese shows the extreme case. The letter ệ is one code point in NFC and three in NFD: e, then the dot below, then the circumflex, in that order, because combining marks sort by how close they sit to the letter.

A trap worth knowing: strokes and ligatures do not decompose at all. ł, ø, đ, æ, œ and ß have no combining form, so a program that strips diacritics by decomposing text will silently leave them untouched. Any real accent stripper needs a hand written map, which is exactly what Remove accents from text does.

Why the marks matter

Because they change meaning, not just sound.

Spanish año means year. Ano means anus. The tilde is doing real work.
French côte is a coast or a rib, cote is a rating, coté is rated, côté is a side. Four words, one base.
Spanish papá is dad, papa is potato. Sí is yes, si is if. Él is he, el is the.
Italian è is “is”, e is “and”.
Czech byt is a flat, být is to be.
Polish łoś is an elk, los is fate.

There is a widespread myth that accents are optional in capital letters. They are not. The Académie française states that accents on capitals are obligatory in French, so it is État and École, not Etat and Ecole. Spanish is the same: Ñ keeps its tilde in a headline.

Where to go next

If you want the marks compared one by one, with the French, Spanish, German and Portuguese rules for each, read Acute, grave, circumflex, tilde, umlaut: the difference. If you keep mixing up the characters that look alike, Common accent mistakes and the confusable characters covers ´ against ’, ø against ö, ß against β and the dashes.

For the practical side, pick your platform: How to type accents on Windows (Alt codes and layouts), How to type accents on a Mac (Option key and press-and-hold), How to type accents on Linux (Compose key), or the reference lists in Alt codes for accented letters: the complete verified list and HTML entity, Unicode and CSS codes for accented letters. Each language hub lists exactly which letters you need, starting with Spanish, French and German, and every individual character has its own page from Accent Letter.