Stress and weak vowels

One of the most important things a non-native speaker must learn is that English has two types of vowels, strong and weak, which are closely related to the presence or absence of stress. But first I need to make it clear that the concept of weak and strong vowel in English has nothing to do with the categories of vocal fuerte and vocal débil  in Spanish, it’s a completely different approach. And, of course, when I refer to vowels I’m talking about sounds (or, more precisely, phonemes), not letters. If I want to mention a letter, I’ll say it explicitly.

Let’s start by looking at the weak vowels, since it’s in this area where the differences between English and Spanish are bigger.

The commonest weak vowel is the schwa /ə/, which is the most frequent sound in English. Two crucial features must be remembered about the schwa:

  1. It only occurs in unstressed syllables.
  2. It can be spelled as almost any vowel letter or combination of vowel letters.

For example, the phoneme in the first syllable of the word about -which bears no stress- is not pronounced as an /a/, as many Spanish speakers tend to think, but as a schwa /əˈbaʊt/ sound_loud_speaker. In the second syllable of the word gorgeous, which is also unstressed, we pronounce a schwa as well.  /ˈɡɔːdʒəs/ sound_loud_speaker

As you can observe, the vowel sounds in these two unstressed syllables are exactly the same, in spite of the fact that you have just one letter (a) in about and three letters (eou) in gorgeous.

How can just a single vowel letter sound the same as a group of three vowel letters? This is a really surprising fact for a non-native speaker, but the sooner you get used to it, the better. The reason is that vowels in unstressed syllables tend to be weakened or, using another term, reduced. This means several things. First, they are produced with less movement of the articulators. The schwa, for example, is produced at the very centre of the mouth, with the tongue completely relaxed and is neither rounded nor spread. Weak vowels are also shorter and softer. The sound is less distinct. Phoneticians talk about obscuration of the vowel, a word which conveys a good image of how it sounds.

From this we can draw a first conclusion: whenever a syllable is not stressed, there is a big chance that the vowel or vowels it contains will be pronounced as a schwa (in a great majority of cases) or as another weak vowel, as we’ll now see.

Which phonemes can be weak? We’ve already said that the quintessential weak vowel is the schwa, but it’s not the only one.

The phoneme /ɪ/ can be both weak and strong. In words like women /ˈwɪmɪn/, minute /ˈmɪnɪt/, ticket /ˈtɪkɪt/ or biscuit /ˈbɪskɪt/, the first /ɪ/ is strong and the second weak.

In captain /ˈkæptɪn/ and manage /ˈmænɪdʒ/, the /ɪ/ is weak too, as is in may function words, such as it /ɪt/, thisɪs/ is /ɪz/, etc.

The capacity for functioning as both weak and strong vowels also applies to the phoneme /ʊ/, but the cases of weak /ʊ/ are not so common, mainly because this phoneme tends to be reduced to a schwa in unstressed syllables. We find a weak  /ʊ/ in the word adulthood /ˈædʌlthʊd/, for example, and if you say beautiful as /ˈbjuːtɪfʊl/, you are using a weak /ʊ/ as well, although this word is most commonly pronounced in its further reduced forms of /ˈbjuːtəfəl/ or /ˈbjuːtəfl/ (the last option is a syllabic consonant, article coming soon).

Finally, there are other two weak sounds, the short /i/ and /u/ (they are not phonemes, but allophones, as explained here).

The short /i/ is extremely common, especially at the end of words: city /ˈsɪti/, country /ˈkʌntri/, basically /ˈbeɪsɪkli/, etc.

It can also be found in the middle of words, mainly before stresses (association /əˌsəʊsiˈeɪʃn/, geography /iˈɒɡrəfi/) and in the article the before vowels, e.g., the accident ǀ ði  ˈæksɪdənt ǀ.

The short /u/ is the sound we use in the particle to before vowels ǀ tu ʌs  ǀ and also in words such as situation /ˌsɪtʃuˈeɪʃən/ or annual /ˈænjuəl/.

Have a look at this example, where the predominance of the schwa is quite obvious.

sound_loud_speaker There was a woman that had brought her daughter with herǀ  ðə wəə ˈwʊmən ðəəd ˈbrɔːə ˈdɔːtə wɪð ə ǀ

In this simple sentence we have thirteen vowel phonemes, of which just three are strong vowels (/ʊ/, /ɔː/, /ɔː/). The remaining ten are weak vowels, nine of them schwas (/ə/) and only one an /ɪ/, which is weak because it’s placed in an unstressed syllable.

Said by a native speaker, this apparently harmless statement can pose a few challenges to Spanish or other non-native speakers. Let’s see them in detail.

  1. When the word there is used to announce the existence of something it’s always unstressed and pronounced with a schwa /ðə/. It’s called the “existential there” and is the equivalent of hay, hubo, habrá, etc. in Spanish.
  2. The letter r is not pronounced in the words there, daughter and her because I speak British  English, a non-rhotic variety, which means that the r is only pronounced when it’s followed by a vowel.
  3. The word was is normally pronounced /wəz/. There is a strong form /wɒz/, but this is just used for emphasis, contrast or at the end of a clause (and please, never say /waz/, as many Spanish speakers do).
  4. Here the word that is pronounced with a schwa (/ðət/) because it’s a conjunction. The strong form (/ðæt/) is used when it’s a demonstrative (that man).
  5. The auxiliary verb have is normally unstressed and pronounced with a schwa. The /h/ is very frequently dropped because of elision. Remember that these three features (unstressed, schwa and elision of /h/) only apply to the auxiliary. When have is a main verb with the meaning of tener, it’s stressed and pronounced in its strong form /hæv/.
  6. In the pronoun her, repeated twice in the sentence, the /h/ is dropped because of elision as well.
  7. There could be another complication in this sentence. In the phrase that had brought, the speaker could have used an assimilation of d to b. It is a very common process and it would sound like this sound_loud_speakerǀ  ðəəb ˈbrɔːt ǀ. 

This is the type of analysis I do with my students in my one-to-one classes. I make them practise these processes with exercises until they improve their comprehension of native speakers and are capable of speaking like that themselves. If you are interested in my classes, you can contact me here.


Reduced vowels in free variation. It’s important to mention that weak vowels can often be used interchangeably in unstressed syllables, especially  /ə/ and /ɪ/. The word animal can be pronounced /ˈænɪməl/ or /ˈænəməl/ without much difference.  Similarly, family can be pronounced /ˈfæmɪli/ or /ˈfæməli/, and also /ˈfæmli/. This last process is called compression (and it’s also the subject of a future article in this website).

A word like signature is particularly interesting. Here too we can use the phonemes /ə/ and /ɪ/ interchangeably in the second syllable (/ˈsɪɡnətʃə/ or /ˈsɪɡnɪtʃə/) and neither of them coincides with the idea a Spanish speaker normally has of how to pronounce this word (usually with an /a/ in the second syllable and an /u/ in the third, something like */ˈsiɡnaur/). Another example: the Oxford online dictionary gives the transcriptions /ˈkrɪmɪnl/ and/ˌkrɪmɪˈnæləti/ for criminal and criminality; on the other hand, Longman agrees on /ˈkrɪmɪnəl/, but provides a slightly different version in /ˌkrɪməˈnæləti/. 

This type of variation also takes place between /ʊ/ and /ə/. The verb speculate can be said /ˈspekjʊleɪt/ or /ˈspekjəleɪt/, and both are completely acceptable (the second displays a higher degree of reduction). There are many other cases in which the combination of phonemes /jʊ/ becomes /jə/ in unstressed syllables.

What you have to remember about these small differences is that their importance is really negligible. Both options are correct and speakers can do as they please.


Strong vowels are all the monophthongs, except the /ə/ (schwa) and  the short /i/ and /u/, plus all the diphthongs and all the triphthongs.

One important thing to take into account is that, although strong vowels are stressed most of the times, they can be found in unstressed syllables too. There are plenty of examples: massage /ˈmæsɑːʒ/, ambassador /æmˈbæsədə/, colleague /ˈkɒlɡ/,  torment /ˈtɔːment/, alternative /ɔːlˈtɜːnətɪv/. All the phonemes in red are strong vowels in unstressed syllables.

It also happens with diphthongs: ideal /ˈdiːəl/, regulate /ˈreɡjult/, blackout /ˈblækt/ obese /əʊˈbiːs/

And, within a clause, we have many examples of diphthongs occupying unstressed positions.

sound_loud_speaker We’re very proud of our daughter. ǀ wɪə ˈveri ˈpraʊd əv aʊə ˈdɔːtə ǀ

sound_loud_speaker My mother was nice. ǀ m ˈmʌðə wəz ˈnaɪs ǀ

When a diphthong is placed in an unstressed syllable the second vowel can be considerably debilitated, often to the point of being dropped altogether, especially in rapid, everyday speech. This is particularly true of the diphthong /əʊ/, like in the following examples (in dictionaries this is sometimes signalled with the second element in italics /əʊ/):

obey /əʊˈbeɪ/ → /əˈbeɪ/

paleolithic  /ˌpæliəʊˈlɪθɪk/ → /ˌpæliəˈlɪθɪk/

There are also other cases of weakened diphthongs, other than /əʊ/. The contraction they’ll is very frequently pronounced /ðel/ instead of /ðl/.

sound_loud_speaker They’ll be here in a moment. ǀ ðel bi ˈhɪər ɪn ə ˈməʊmənt ǀ 

We’re  /wɪəis often reduced reduced to /wi/.

sound_loud_speaker We’re considering moving out.  ǀ wkənˈsɪdərɪŋ ˈmuːvɪŋ ˈaʊt ǀ

Let’s read what professor Adrian Underhill has to say about this: “Unstressed diphthongs become generally less distinct, often losing their two-vowel glide quality and merging into one composite `greyish´ monophthong”.