Why do people have Accents?
An accent is the general term in phonetics and linguistics for the sound qualities in speech that give more prominence to one syllable than to others in a word, or more emphasis to one part of a group of words. Accent may be the only difference in sound that signals a difference in meaning between two similar utterances. For example, in English the words permit (certificate of permission) and permit (to allow) are differentiated only by accent.
The Three Voice-Qualities
Accent may be carried by one or more of three voice-qualities: loudness, pitch, and duration of sound. Accent by voice-loudness is usually called stress; accent by voice-pitch is called tone; and accent by the relative length of sound is called quantity. To some extent, every language has all three of these qualities. English and the other Germanic languages characteristically use a very strong stress accent. Chinese, Thai, and most African languages use primarily a pitch accent to distinguish similar words or the grammatical functions of words; as a consequence, they are called tone languages. Quantity is not prominent in any particular language or group of languages, but Italian, Swedish, and Ojibwa, among others, have vowel length as one differentiating element.
Development of Accent
Indo-European, the language from which the speech of Europe, much of the Middle East, and much of India is descended, had a pitch accent that could occupy various places in a word. In the development of the subfamilies of Indo-European the movable pitch accent was replaced by a fixed stress accent. This process was fundamental in bringing about the immense differences between such languages as Norwegian and Armenian, for example. Both are Indo-European languages, but it is almost impossible for anyone but a linguist to demonstrate the kinship between them. A cardinal achievement of 19th century linguistics was the demonstration by the Danish philologist Karl Verner that certain confusions in the history of the Germanic languages could be clarified by showing the position of the accents in the Indo-European roots.
As far back as the English language can be traced, it has had four levels of stress— primary, secondary, tertiary, and weak. In speech a one-syllable word by itself has primary stress (car), two-syllable words usually have primary and weak (above, angel), and multisyllable words have primary, tertiary, and weak (celebrate). Secondary stress almost never occurs in single words, but it is used to differentiate between similar pairs, such as rotten-stone and rotten stone.
Pitch accent on single words is not characteristic of English, but pitch is crucial in expressions where intonation determines meaning. For example, the difference between "John!" and "John?" and between "Am I happy!" and "Am I happy?" is signaled chiefly by pitch.