In articulatory phonetics, the manner of articulation is the configuration and interaction of the articulators (speech organs such as the tongue, lips, and palate) when making a speech sound. One parameter of manner is stricture, that is, how closely the speech organs approach one another. Others include those involved in the r-like sounds (taps and trills), and the sibilancy of fricatives.
The concept of manner is mainly used in the discussion of consonants, although the movement of the articulators will also greatly alter the resonant properties of the vocal tract, thereby changing the formant structure of speech sounds that is crucial for the identification of vowels. For consonants, the place of articulation and the degree of phonation or voicing are considered separately from manner, as being independent parameters. Homorganic consonants, which have the same place of articulation, may have different manners of articulation. Often nasality and laterality are included in manner, but some phoneticians, such as Peter Ladefoged, consider them to be independent.
Manners of articulation with substantial obstruction of the airflow (stops, fricatives, affricates) are called obstruents. These are prototypically[clarification needed] voiceless, but voiced obstruents are extremely common as well. Manners without such obstruction (nasals, liquids, approximants, and also vowels) are called sonorants because they are nearly always voiced. Voiceless sonorants are uncommon, but are found in Welsh and Classical Greek (the spelling "rh"), in Standard Tibetan (the "lh" of Lhasa), and the "wh" in those dialects of English that distinguish "which" from "witch".
Sonorants may also be called resonants, and some linguists prefer that term, restricting the word 'sonorant' to non-vocoid resonants (that is, nasals and liquids, but not vowels or semi-vowels). Another common distinction is between occlusives (stops, nasals and affricates) and continuants (all else).
From greatest to least stricture, speech sounds may be classified along a cline as stop consonants (with occlusion, or blocked airflow), fricative consonants (with partially blocked and therefore strongly turbulent airflow), approximants (with only slight turbulence), tense vowels, and finally lax vowels (with full unimpeded airflow). Affricates often behave as if they were intermediate between stops and fricatives, but phonetically they are sequences of a stop and fricative.
Over time, sounds in a language may move along the cline toward less stricture in a process called lenition or towards more stricture in a process called fortition.
Sibilants are distinguished from other fricatives by the shape of the tongue and how the airflow is directed over the teeth. Fricatives at coronal places of articulation may be sibilant or non-sibilant, sibilants being the more common.
Flaps (also called taps) are similar to very brief stops. However, their articulation and behavior are distinct enough to be considered a separate manner, rather than just length. The main articulatory difference between flaps and stops is that, due to the greater length of stops compared to flaps, a build-up of air pressure occurs behind a stop which does not occur behind a flap. This means that when the stop is released, there is a burst of air as the pressure is relieved, while for flaps there is no such burst.
Trills involve the vibration of one of the speech organs. Since trilling is a separate parameter from stricture, the two may be combined. Increasing the stricture of a typical trill results in a trilled fricative. Trilled affricates are also known.
Nasal airflow may be added as an independent parameter to any speech sound. It is most commonly found in nasal occlusives and nasal vowels, but nasalized fricatives, taps, and approximants are also found. When a sound is not nasal, it is called oral.
Laterality is the release of airflow at the side of the tongue. This can be combined with other manners, resulting in lateral approximants (such as the pronunciation of the letter L in the English word "let"), lateral flaps, and lateral fricatives and affricates.
All of these manners of articulation are pronounced with an airstream mechanism called pulmonic egressive, meaning that the air flows outward, and is powered by the lungs (actually the ribs and diaphragm). Other airstream mechanisms are possible. Sounds that rely on some of these include: