An affricate is a consonant that begins as a stop and releases as a fricative, generally with the same place of articulation (most often coronal). It is often difficult to decide if a stop and fricative form a single phoneme or a consonant pair.[1] English has two affricate phonemes, /t͡ʃ/ and /d͡ʒ/, often spelled ch and j, respectively.

The English sounds spelled "ch" and "j" (broadly transcribed as [t͡ʃ] and [d͡ʒ] in the IPA), German and Italianz[t͡s] and Italianz[d͡z] are typical affricates, and sounds like these are fairly common in the world's languages, as are other affricates with similar sounds, such as those in Polish and Chinese. However, voiced affricates other than [d͡ʒ] are relatively uncommon. For several places of articulation they are not attested at all.

Much less common are labiodental affricates, such as [p͡f] in German and Izi, or velar affricates, such as [k͡x] in Tswana (written kg) or in High Alemannic Swiss German dialects. Worldwide, relatively few languages have affricates in these positions even though the corresponding stop consonants, [p] and [k], are common or virtually universal. Also less common are alveolar affricates where the fricative release is lateral, such as the [t͡ɬ] sound found in Nahuatl and Navajo. Some other Athabaskan languages, such as Dene Suline, have unaspirated, aspirated, and ejective series of affricates whose release may be dental, alveolar, postalveolar, or lateral: [t̪͡θ], [t̪͡θʰ], [t̪͡θʼ], [t͡s], [t͡sʰ], [t͡sʼ], [t͡ʃ], [t͡ʃʰ], [t͡ʃʼ], [t͡ɬ], [t͡ɬʰ], and [t͡ɬʼ].

Affricates are transcribed in the International Phonetic Alphabet by a combination of two letters, one for the stop element and the other for the fricative element. In order to show that these are parts of a single consonant, a tie bar is generally used. The tie bar appears most commonly above the two letters, but may be placed under them if it fits better there, or simply because it is more legible.[2] Thus:

⟨p͡f, t͡s, d͡z, t͡ɬ, d͡ɮ, t͡ʃ, d͡ʒ, t͡ɕ, d͡ʑ, ʈ͡ʂ, ɖ͡ʐ , k͡x⟩

or

⟨p͜f, t͜s, d͜z, t͜ɬ, d͜ɮ, t͜ʃ, d͜ʒ, t͜ɕ, d͜ʑ, ʈ͜ʂ, ɖ͜ʐ , k͜x⟩.

A less common notation indicates the release of the affricate with a superscript:

⟨pᶠ, tˢ, dᶻ, tᶴ, dᶾ, kˣ⟩

This is derived from the IPA convention of indicating other releases with a superscript. However, this convention is more typically used for a fricated release that is too brief to be considered a true affricate.

Though they are no longer standard IPA, ligatures are available in Unicode for eight common affricates

⟨ʦ ʣ, ʧ ʤ, ʨ ʥ, ꭧ ꭦ⟩.

Any of these notations can be used to distinguish an affricate from a sequence of a stop plus a fricative, which exists in some languages such as Polish. However, in languages where there is no such distinction, such as English, the tie bars are commonly dropped.

In other phonetic transcription systems, such as the Americanist system, affricates may be transcribed with single letters. The affricates [t͡s], [d͡z], [t͡ʃ], [d͡ʒ], [t͡ɬ], [d͡ɮ] are transcribed respectively as ⟨c⟩ or ⟨¢⟩; ⟨j⟩, ⟨ƶ⟩, or (older) ⟨ʒ⟩; ⟨c⟩ or ⟨č⟩; ⟨ǰ⟩, ⟨ǧ⟩, or (older) ⟨ǯ⟩; ⟨ƛ⟩; and ⟨λ⟩ or ⟨dl⟩. Within the IPA, [tʃ] and [dʒ] are sometimes transcribed with the symbols for the palatal stops, ⟨c⟩ and ⟨ɟ⟩.

The exact phonetic difference varies between languages. In stop–fricative sequences, the stop has a release burst before the fricative starts; but in affricates, the fricative element is the release. Phonologically, stop–fricative sequences may have a syllable boundary between the two segments, but not necessarily.

In English, /ts/ and /dz/ (nuts, nods) are considered phonemically stop–fricative sequences. They often contain a morpheme boundary (for example, nuts = nut + s). The English affricate phonemes /t͡ʃ/ and /d͡ʒ/ do not generally contain morpheme boundaries. Depending on dialect, English speakers may distinguish an affricate from a stop–fricative sequence in some contexts such as when the sequence occurs across syllable boundaries:

bent shudder/bɛnt.ʃʌdəɹ/ → [bɛnʔʃʌdəɹ]

bench udder/bɛnt͡ʃ.ʌdəɹ/ → [bɛnt͡ʃʌdəɹ]

The /t/ in 'bent shudder' debuccalizes to a glottal stop before /ʃ/ in many dialects, making it phonetically distinct from /t͡ʃ/.

One acoustic criterion for differentiating affricates and stop–fricative sequences is the rate of amplitude increase of the frication noise, which is known as the rise time. Affricates have a short rise time to the peak frication amplitude; stop–fricative sequences have longer rise times (Howell & Rosen 1983, Johnson 2003, Mitani et al. 2006).

The Northwest Caucasian languages Abkhaz and Ubykh both contrast sibilant affricates at four places of articulation: alveolar, postalveolar, alveolo-palatal and retroflex. They also distinguish voiceless, voiced, and ejective affricates at each of these.

When a language only has one type of affricate, it is usually a sibilant; this is the case in e.g. Arabic ([d̠ʒ]), most dialects of Spanish ([t̠ʃ]), and Thai ([tɕ]).

The more common of the voiceless affricates are all attested as ejectives as well: [tθʼ, tsʼ, tɬʼ, tʃʼ, tɕʼ, tʂʼ, cʎ̥ʼ, kxʼ, kʟ̝̊ʼ]. Several Khoisan languages such as !Xóõ are reported to have voiced ejective affricates, but these may actually be consonant clusters: [dtsʼ, dtʃʼ]. Affricates are also commonly aspirated: [ɱp̪fʰ, tθʰ, tsʰ, tɬʰ, tʃʰ, tɕʰ, tʂʰ], occasionally murmured: [ɱb̪vʱ, d̠ʒʱ], and sometimes prenasalized: [ⁿdz, ⁿdzʱ, ᶯɖʐ, ᶯɖʐʱ]. Labialized, palatalized, velarized, and pharyngealized affricates also occur. Affricates may also have phonemic length, that is, affected by a chroneme, as in Italian and Karelian.

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In phonology, affricates tend to behave similarly to stops, taking part in phonological patterns that fricatives do not. Kehrein analyzes phonetic affricates as phonological stops.[6] A sibilant or lateral (and presumably trilled) stop can be realized phonetically only as an affricate and so might be analyzed phonemically as a sibilant or lateral stop. In that analysis, affricates other than sibilants and laterals are a phonetic mechanism for distinguishing stops at similar places of articulation (like more than one labial, coronal, or dorsal place). For example, Chipewyan has laminal dental [t̪͡θ] vs. apical alveolar [t]; other languages may contrast velar [k] with palatal [c͡ç] and uvular [q͡χ].
Affricates may also be a strategy to increase the phonetic contrast between aspirated or ejective and tenuis consonants.

According to Kehrein, no language contrasts a non-sibilant, non-lateral affricate with a stop at the same place of articulation and with the same phonation and airstream mechanism, such as /t̪/ and /t̪θ/ or /k/ and /kx/.

In rare instances, a fricative–stop contour may occur. This is the case in dialects of Scottish Gaelic that have velar frication [ˣ] where other dialects have pre-aspiration. For example, in the Harris dialect there is [ʃaˣkʰ] 'seven' and [əhʷɔˣkʰ] 'eight' (or [ʃax͜kʰ], [əhʷɔx͜kʰ]).[10]