Degrees of stress

Primary and secondary stress are distinguished in some languages. English is commonly believed to have two levels of stress, as in the words cóunterfòil [ˈkaʊntɚˌfɔɪl] and còunterintélligence [ˌkaʊntɚ.ɪnˈtɛlɪdʒəns], and in some treatments has even been described as having four levels, primary, secondary, tertiary, and quaternary, but these treatments often disagree with each other.

Phoneticians such as Peter Ladefoged believe these multiple levels are mere phonetic detail and not true phonemic stress. They report that often the alleged secondary stress is not characterized by the increase in respiratory activity normally associated with stress. In their analysis, an English syllable may be either stressed or unstressed, and if unstressed, the vowel may be either full or reduced. This is all that is required for a phonemic treatment. In addition, the last stressed syllable in a normal (default) intonation unit receives additional intonational or "tonic" stress. (The intonational stress may occur elsewhere to mark contrast or other prosodic effects.) This combination of lexical stress, phrase- or clause-final prosody, and the reduction of some unstressed vowels conspires to create the impression of multiple levels of phonetic stress:

* Lexical stress

1. Plus tonic stress: A syllable with both lexical and prosodic stress in Ladefoged's account corresponds to primary stress in the traditional account.
2. Without tonic stress: A syllable with only lexical stress corresponds to secondary stress in the traditional account.

* No stress

3. On a full vowel: An unstressed syllable with a full vowel also corresponds to secondary stress in the traditional account, and to tertiary stress in the fuller account.
4. On a reduced vowel: An unstressed syllable with a reduced vowel is said be unstressed or to have quaternary stress.

Therefore, in a phonemic transcription of English words that indicates reduced vowels like schwa, only a single symbol for stress is required. For example, cóunterfòil is only stressed on the first syllable, /ˈkaʊntɚ.fɔɪl/; the last syllable is an unstressed but unreduced vowel. (Unstressed oi does not normally reduce in English.) In còunterintélligence both marked syllables are stressed, /ˈkaʊntɚ.ɪnˈtɛlɪdʒəns/. The apparent differences in stress are due to prosody and appear when the words are said alone in citation, as, ironically, they are when being sounded out for transcription. They disappear when the words are moved to non-final position, for example in counterintelligence operations are going well, where only well has "primary" stress. (For some speakers, the first syllable of counterintelligence may be unstressed but unreduced, /kaʊntɚ.ɪnˈtɛlɪdʒəns/. Unstressed ou/ow does not normally reduce in English.)