Inlinguistics, aprosodic unit is a segment of speech that occurs with specific prosodic properties. These properties can be those of stress,intonation (a singlepitch andrhythm contour), ortonal patterns.

Prosodic units occur at ahierarchy of levels, from thesyllable, themetrical foot andphonological word to theintonational unit (IU) and to a completeutterance.^[1] However, the term is often restricted to intermediate levels which do not have a dedicated terminology. Prosodic units do not generally correspond to syntactic units, such asphrases andclauses; it is thought that they reflect different aspects of how the brain processes speech, with prosodic units being generated through on-line^{[definition needed]} interaction and processing, and with morphosyntactic units being more automated.

Prosodic units are characterized by several phonetic cues, such aspitch movement, pre-boundary lengthening, and pauses.^[2]Breathing, both inhalation and exhalation, only occurs at the boundaries (pausa) between higher units. Several short contours may carry an additional overall gradual decline in pitch and slowing of tempo; this larger unit is termed adeclination unit (DU). At the boundaries (pauses) between declination units, the pitch and temporeset; for this reason the final one of the shorter internal contours is said to havefinal prosody, whereas the others are said to havecontinuing prosody.

These two levels of thehierarchy may be schematized as follows:

Declination unit
continuing IU,	continuing IU,	continuing IU,	final IU.

In English orthography, acontinuing prosodic boundary may be marked with a comma (assuming the writer is using commas to represent prosody rather than grammatical structure), whilefinal prosodic boundaries may be marked with a full stop (period).

TheInternational Phonetic Alphabet has symbols (single and double pipes) for "minor" and "major" prosodic breaks. Since there are more than two levels of prosodic units, the use of these symbols depends on the structure of the language and which information the transcriber is attempting to capture. Very often, each prosodic unit will be placed in a separate line of the transcription. Using the single and double pipes to mark continuing and final prosodic boundaries, we might have American English,

Jack,

preparing the way,

went on.

[ˈdʒæk|pɹəˌpɛəɹɪŋðəˈweɪ|wɛntˈɑn‖]

or French,

Jacques,

préparant le sol,

tomba.

[ˈʒak|pʁepaʁɑ̃lɵˈsɔl|tɔ̃ˈba‖]

The last syllable with a full vowel in aFrench prosodic unit is stressed, and the last stressed syllable in anEnglish prosodic unit hasprimary stress. This shows that stress is notphonemic in French, and that the difference between primary and secondary stress is not phonemic in English; they are both elements of prosody rather than inherent in the words.

The pipe symbols – thevertical bars| and‖ – used above are phonetic, and so will often disagree with English punctuation, which only partially correlates with prosody.

However, the pipes may also be used formetrical breaks – a single pipe being used to mark metrical feet, and a double pipe to mark both continuing and final prosody, as their alternate IPA descriptions "foot group" and "intonation group" suggest. In such usage, each foot group would include one and only oneheavy syllable. In English, this would mean one and only one stressed syllable:

Jack,

preparing the way,

went on.

[ˈdʒæk‖pɹəˌpɛəɹɪŋ|ðəˈweɪ‖wɛntˈɒn‖]

In many tone languages withdowndrift, such asHausa, the single pipe ⟨|⟩ may be used to represent a minor prosodic break that does not interrupt the overall decline in pitch of the utterance, while ⟨‖⟩ marks either continuing or final prosody that creates apitch reset. In such cases, some linguists use only the single pipe, with continuing and final prosody marked by a comma and period (full stop), respectively. The major break mark may also be doubled, ⟨‖‖⟩, for the most salient (full stop) breaks.

In transcriptions of non-tonal languages, the three symbols – pipe, comma, and period – may also be used, with the pipe representing a break more minor than the comma, the so-calledlist prosody often used to separate items when reading lists, spelling words, or giving out telephone numbers.In Eastern European tradition, the non-IPA dotted line ⟨⸽⟩ may be used for list prosody, and the non-IPA wavy line ⟨⸾⟩ for an unexpected interruption or breaking off of speech, which is indicated with a final hyphen when common punctuation is used.

While each prosodic unit may carry a large information load in rehearsed speech, in extemporaneous conversation the amount of information is much more limited. There is seldom more than a singlelexical noun in any one IU, and it is uncommon to have both a lexical noun and a lexical verb in the same IU. Indeed, many IUs are semantically empty, taken up by filler words such asum, well, ory'know. Chafe (1994) believes that this reflects the constraints of information processing by the brain during speech production, with chunks of speech (IUs) corresponding to chunks of cognitive output. It is also a possibility that the distribution of information across IUs is designed to maximize language comprehension by the other party.

• Phonological hierarchy
• Tone terracing
• Upstep

• Chafe, Wallace (1994).Discourse, Consciousness, and Time: The flow and displacement of conscious experience in speaking and writing. University of Chicago Press.
• Dubois, John W., Susanna Cumming, Stephan Schuetze-Coburn, Danae Paolino eds. (1992).Discourse Transcription. Volume 4 of theSanta Barbara Papers in Linguistics.