The acute accent, ◌́,
is a diacritic used in many modern written languages with alphabets based on the Latin, Cyrillic, and Greek scripts. For the most commonly encountered uses of the accent in the Latin and Greek alphabets, precomposed characters are available.
A sample extract of Icelandic.
A diacritic is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek διακριτικός, from διακρίνω. The word diacritic is a noun, though it is sometimes used in an attributive sense, whereas diacritical is only an adjective. Some diacritics, such as the acute ⟨á⟩, grave ⟨à⟩, and circumflex ⟨â⟩, are often called accents. Diacritics may appear above or below a letter or in some other position such as within the letter or between two letters.
Hangul, the Korean alphabet
German keyboard with umlaut letters
Blackboard used in class at Harvard shows students' efforts at placing the ü and acute accent diacritic used in Spanish orthography.