A syllable is a unit of sound which includes a vowel sound. All words have at least one syllable. A syllable is a unit of speech. For example, the word “potato” is broken up into three parts, or syllables. To comprehend syllables, it helps to understand word stress. All words of more than one syllable have what is called word stress. Stress is an accent that we make on certain syllables and words when speaking English. This means that at least one of the syllables is longer and louder than the other syllables. English words that have more than one syllable (polysyllabic) always have only one syllable that is stressed. The stressed syllable is indicated by a stress mark, a symbol that resembles an apostrophe in the majority of English dictionaries. The stress mark follows the syllable that is stressed. Putting the stress in the correct position of a syllable when speaking is crucial since by putting it otherwise, may cause the listener to mishear or even misunderstand the word. Studying stress patterns in English is particularly important for speakers of other languages whose stress rules are more regular and/or different (Celce-Murcia et al, 1996) and thus interfere with comprehensibility. Stressing the incorrect syllable in a word can make the word very hard to hear and understand. The meaning or type of the word can change when the words are stressed wrongly. Mistakes that make in word stress are a common cause of misunderstanding in English. For example; take three words: contribute, contributor, contribution. Do they sound the same when spoken? No, because one syllable in each word is stressed (stronger than the others) CON tribute, Con TRI butor, Contri BU tion. The acoustic properties of the stressed syllables in English are different from those of the ++unstressed syllables. The unstressed syllables have a weaker vowel and often include the schwa. Visually, when we produce word stress our lips and chins move more (Scarborough, Keating, Mattys, Cho & Alwan, 2009). Accordingly, the vowel is fuller than in non-stressed syllables where it is weaker and therefore requires less mouth opening (as cited in Simarmata, p. 2.3.4).