The acute accent ( ´ ) is a mark in many written languages.  It is usually added above a vowel to show how to say it.  Acute accents are sometimes added to consonants too. Sometimes, the acute accent changes the sound of the whole word by giving it stress in a sentence. This accent is part of many modern languages that use Latin, Cyrillic, and Greek alphabets. The acute accent is one of many similar marks called diacritics.

History
The acute accent was first used in Ancient Greece. It told the speaker when to say a syllable with a high pitch. Another early accent mark was the apex. In Latin the apex marked long vowels.

Uses

Sounds
The acute accent is mainly used to tell readers about the sound of vowels in words. Sometimes it is very important to the meaning because it shows the difference between two similar words. For example, resume may mean to start again, but résumé is a summary of someone's work and school experience. Some languages use the accent to show the same changes in sounds, but others use it differently. The acute accent may show:
 the vowel is stressed;
 the vowel height of some stressed vowels in many Romance languages;
 long vowels;
 the tone in languages such as Vietnamese or Mandarin Chinese written in pinyin;
 or, the pitch, or high accent, in dictionaries or language learning textbooks.

Expanding the alphabet 

Some languages use the accent to actually make new letters. Both Faroese and Icelandic add the acute accent to all of their vowels to make new letters. These letters, á, í, ó, ú and ý (plus é in Icelandic) are separate letters with different pronunciations. In Turkmen, the letter  is a consonant: .

French words in other languages 
Many languages have borrowed words from French. Many Norwegian words which came from French keep an acute accent. Some examples are: allé, kafé, idé, komité.  Swedish examples include café and resumé (noun). Examples in English include: attaché, canapé, cliché, communiqué, café, décor, fiancé, passé, toupée and touché. However, sometimes writers forget or choose not to use the accent mark.

Writing other languages in English
Some languages such as Arabic, Persian, or Japanese do not use alphabets. Some writers use the acute accent to tell how the words should sound when words from these languages are written in English. This is more common in older books and less common today.

Technical notes 
The ISO-8859-1 and Windows-1252 character encodings included á, é, í, ó, ú, ý. They also had how letters and accents looked when they were written as capital letters. Unicode has many more letters with the acute accent.

Microsoft Office
To make an accented letter in a Microsoft Office software (Word, PowerPoint, Excel, etc.), users hold the  key and press the apostrophe  key once. Then, let the  key go, and press the letter they want.

Macintosh OS X
On Apple Macintosh computers, users press option-e and then the vowel. Vowels can also be capitalised. For example, users make á by pressing option-e and then 'a'. Pressing Option-e and then Shift-a makes Á.

Web
On Wikipedia, users make these symbols by clicking on a link in a box. Some other websites work the same way.

Related pages
 Circumflex accent
 Font
 Grave accent
 International Phonetic Alphabet (IPA)
 Typography

References

Other websites
Diacritics Project – All you need to design a font with correct accents
Keyboard Help – Learn how to create world language accent marks and other diacriticals on a computer

Alphabetic diacritics