Sentence Stress

In English, stress also influences how sentences and incomplete sentences are pronounced. We say different parts of the sentence with more or less stress, i.e.  slower and louder or quicker and more softly. This is called sentence stress. One word in the sentence has main stress. This is the word which the speaker thinks is most important to the meaning of the sentence. Other words can have secondary stress.  This is not so strong as the main stress and falls on words which are not so important to the meaning as the word with main stress. Other words in the sentence are unstressed. For example, in “She came home late last night” or “I can’t understand a word he says”, the words with the mains stress are the underlined ones, the words with secondary stress would probably be came, home, last, night, and can’t, understand, says, and the unstressed words she and I, a, he.

Main and secondary stress are usually on content words(verbs, adjectives, nouns, they give more information) rather than structural words(articles, prepositions, grammar words)

Changing the stress of a sentence changes its meaning

Look at these examples:

The girl ran to the sea and jumped in quickly (i.e. not another person)

The girl ran to the sea and jumped in quickly (i.e. not to any other place)          

The girl ran to the sea and jumped in quickly (i.e. not in any other way)

Sentence stress is a characteristic of connected speech, i.e. spoken language in which all the words join to make a connected stream of sounds

Taken from “The TKT Course”, Spratt, Pulverness, Williams, Cambridge University Press

English is a stress timed language

The English language is often referred to as stress-timed. This means that stress in a spoken sentence occurs at regular intervals and the length it takes to say something depends on the number of stressed syllables rather than the number of syllables itself

Try saying the sentences below

1                                         2                                               3                                             4

1  and                                2  and                                     3   and                                   4

1 and a                              2  and a                                  3 and a                                 4

1 and then a                    2  and then a                        3 and then a                        4

The four sentences take the same length of time to say and you will notice the numbers are stressed and the unstressed words in between are said much more quickly in order to keep the rhythm of the language. In other languages, which are not stress-timed the stress would fall more equally on each word and syllable.”

http://esol.britishcouncil.org/teaching-pronunciation/sentence-stress