Phoneticians divide syllables into strong (heavy) and weak (light). A strong syllable contains a long vowel or a diphthong or a short vowel plus two consonants; syllables with a short vowel and no coda are weak ones. Only strong syllables can be stressed (although not all of them), but weak syllables are never stressed.
Factors that may determine the placement of stress are: the morphological structure of the word (whether it is simple, complex or compound), its grammatical category (noun, verb, adjective, etc. The word stress in English as well as in Russian is not only free, but it may also be shifting, thus differentiating lexical units, parts of speech and grammatical forms: ˈcontrast - conˈtrast, ˈtransport - transˈport, ˈзамок - заˈмок, ˈмука - муˈка) and the number of syllables in the word.
Besides the stress pattern of English words can vary under the influence of some factors. First of all in the present day English stress can shift under the influence of rhythm to avoid a succession of weak syllables (stress shifts to the second syllable, or the third one from the end) as in ˈhospitable - hosˈpitable, disˈtribute - ˈdistribute, ˈaristocrat - aˈristocrat, etc. In compounds the stress on a final-stressed compound tends to move to a preceding syllable if the following word begins with a strongly stressed syllable: afterˈnoon - ˈafternoon ˈtea.
The stress pattern can change under the influence of tempo as well; in this case secondary stresses are dropped. It sometimes happens that a word’s stress pattern is influenced not only by rhythm, but also by the stress structure of a derivative: preˈfer - preˈferable (instead of the regular ˈpreferable; ˌdistriˈbution - ˈdistribute (instead of the regular diˈstribute).
There are three degrees of word stress: primary - the strongest, secondary and weak (or unstressed): eˌxamiˈnation, ˌorganiˈsation. Some linguists also distinguish