Diacritics are marks placed above or below (or sometimes next to) a letter in a word to indicate a particular pronunciation—in regard to accent, tone, or stress—as well as meaning, especially when a homograph exists without the marked letter or letters. For example, pâte refers to clay whereas pate refers to the head, and résumé or resumé is used for a work history versus resume, which means "to begin again."
Diacritical marks take such forms as a straight or curvy line or a dot or a pair of dots, and they are an integral part of spelling in many foreign languages. In English, words having diacritics are borrowings from other languages, and the marks are not a natural part of the English language itself. However, lexicographers have adopted diacritics to indicate English pronunciation and, of course, to show word etymologies. Although the English borrowings enter the language with their markings, they are often dropped from many spellings through Anglicization. Take, for instance, French naïve, which is commonly spelled naive in English.
The word diacritic is a derivative of Greek diakritikos, meaning "separative" or "able to distinguish," which is based on the prefix dia-, meaning "through" or "across," and the verb krinein, "to separate." The word was first used as an adjective in 17th-century English with the meaning "serving to distinguish" (as in "diacritic factors in demography"). It wasn't until the 19th century that it began being used as the name for a phonological diacritical (the '-al' spelling of the adjective being the most common) mark.
Diacritical marks are important in correctly pronouncing many foreign words that have migrated into the English language. Being a publisher of references on the English language, we feel it is important to give a tutorial on the more common diacritics that you will encounter in your pursuit of knowledge through reading. So, without further ado, let's begin.