Consonants - English does not have more individual consonant sounds than most languages. However, /θ/ and /ð/ (the sounds written with th), which are common in English (thin, thing, etc.; and the, this, that, etc.) are relatively rare in other languages, even others in the Germanic family (e.g., English thousand = German tausend). Many learners substitute a [t] or [d] sound that is more natural for them. Even practiced second language speakers, like many francophone Canadian politicians, carry on this habit long after mastering vocabulary and grammar. Another sound that is relatively uncommon in other languages is /ŋ/ (as in singing). The learner’s task is further complicated by the fact that native speakers may drop consonants in the more complex blends in certain positions (e.g.,[məns] instead of [mənθs] for months).
Vowels - English has a moderate number of distinct vowel sounds, although not all are phonemic. The precise number depends on the variety of English: for example, Received Pronunciation has twelve monophthongs (single or “pure” vowels), eight diphthongs (double-vowel blends) and two triphthongs (triple-vowel blends); whereas American English is simpler, with only eleven monophthongs and three diphthongs. Learners whose native languages have simpler vowel systems (e.g., Arabic or Japanese) may have trouble with English vowel distinctions.
Syllable structure - In its syllable structure, English allows for a cluster of up to three consonants before the vowel and four consonants after the vowel (e.g.,straw, desks, glimpsed). The syllable structure causes problems for speakers of many other languages. Japanese, for example, alternates consonant and vowel sounds so learners from Japan often try to force vowels in between the consonants (e.g.,desks/desks/ becomes "desukusu" or milk shake/mlk ek/ becomes "mirukusēki"). Learners from languages where all words end in vowels (e.g., Italian) tend to make all English words end in vowels - make/mek/ comes out as [mekə]. Speakers of Germanic and Slavic languages have fewer difficulties in this area.
Unstressed vowels - Native English speakers frequently replace a long or short vowel with an unstressed vowel, often schwa, in an unstressed syllable. For example, from has a distinctly pronounced short 'o' sound when it is stressed (e.g.,Where are you from?), but when it is unstressed, the short 'o' reduces to a schwa (e.g.,I'm from London.). In English stress more bly determines vowel quality than it does in most other world languages (although there are notable exceptions like Russian). To a learner, this means that the syllables an, en, in, on and un may sound exactly alike. A native speaker can usually distinguish an able, enable, and unable because of their position in a sentence, but this is more difficult for inexperienced English speakers. Moreover, learners tend to overpronounce these unstressed vowels, making their speech sound strained and out of rhythm.
Stress timing - English tends to be a stress-timed language - this means that stressed syllables are roughly equidistant in time, no matter how many syllables come in between. Although some other languages,e.g., German and Russian, are also stress-timed, most of the world's other major languages are syllable-timed, with each syllable coming at an equal time after the previous one. These learners can develop a staccato rhythm when speaking English that is disconcerting to a native speaker.
Connected speech - Phonological processes such as assimilation, elision and epenthesis together with indistinct word boundaries can confuse learners when listening to natural spoken English, as well as making their speech sound too formal if they do not use them.
