Voiced palatal approximant
The voiced palatal approximant, or yod, is a type of consonant used in many spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨j⟩. The equivalent X-SAMPA symbol is
j, and in the Americanist phonetic notation it is ⟨y⟩. Because the English name of the letter J, jay, starts with [d͡ʒ] (voiced palato-alveolar affricate), the approximant is sometimes instead called yod (jod), as in the phonological history terms yod-dropping and yod-coalescence.
The palatal approximant can often be considered the semivocalic equivalent of the close front unrounded vowel [i]. They alternate with each other in certain languages, such as French, and in the diphthongs of some languages as ⟨j⟩ and ⟨i̯⟩, with the non-syllabic diacritic used in different phonetic transcription systems to represent the same sound.
Some languages, however, have a palatal approximant that is unspecified for rounding and so cannot be considered the semivocalic equivalent of either [i] or its rounded counterpart, [y], which would normally correspond to [ɥ]. An example is Spanish, which distinguishes two palatal approximants: an approximant semivowel [j], which is always unrounded, and an unspecified for rounding approximant consonant [ʝ̞]. Eugenio Martínez Celdrán describes the difference between them as follows (with audio examples added):
[j] is shorter and is usually a merely transitory sound. It can only exist together with a full vowel and does not appear in syllable onset. [On the other hand,] [ʝ̞] has a lower amplitude, mainly in F2. It can only appear in syllable onset. It is not noisy either articulatorily or perceptually. [ʝ̞] can vary towards [ʝ] in emphatic pronunciations, having noise (turbulent airstream). (...) There is a further argument through which we can establish a clear difference between [j] and [ʝ̞]: the first sound cannot be rounded, not even through co-articulation, whereas the second one is rounded before back vowels or the back semi-vowel. Thus, in words like viuda 'widow', Dios 'God', vio 's/he saw', etc., the semi-vowel [j] is unrounded; if it were rounded a sound that does not exist in Spanish, [ɥ], would appear. On the other hand, [ʝ̞] is unspecified as far as rounding is concerned and it is assimilated to the labial vowel context: rounded with rounded vowels, e.g. ayuda 'help', coyote 'coyote', hoyuelo 'dimple', etc., and unrounded with unrounded vowels: payaso 'clown', ayer 'yesterday'.
He also considers that "the IPA shows a lack of precision in the treatment it gives to approximants, if we take into account our understanding of the phonetics of Spanish. [ʝ̞] and [j] are two different segments, but they have to be labelled as voiced palatal approximant consonants. I think that the former is a real consonant, whereas the latter is a semi-consonant, as it has traditionally been called in Spanish, or a semi-vowel, if preferred. The IPA, though, classifies it as a consonant."
There is a parallel problem with transcribing the voiced velar approximant.
The symbol ⟨ʝ̞⟩ may not display properly in all browsers. In that case, ⟨ʝ˕⟩ should be substituted.
In the writing systems used for most languages in Central, Northern, and Eastern Europe, the letter j denotes the palatal approximant, as in German Jahr 'year'. That is followed by IPA although it may be counterintuitive for English-speakers although words occur with that sound in a few loanwords in English like Hebrew "hallelujah" and German "Jägermeister".
In grammars of Ancient Greek, the palatal approximant, which was lost early in the history of Greek, is sometimes written as ⟨ι̯⟩, an iota with the inverted breve below, which is the nonsyllabic diacritic or marker of a semivowel.
There is also the post-palatal approximant in some languages, which is articulated slightly more back than the place of articulation of the prototypical palatal approximant but less far back than the prototypical velar approximant. It can be considered the semivocalic equivalent of the close central unrounded vowel [ɨ]The International Phonetic Alphabet does not have a separate symbol for that sound, but it can be transcribed as ⟨j̠⟩, ⟨j˗⟩ (both symbols denote a retracted ⟨j⟩), ⟨ɰ̟⟩ or ⟨ɰ˖⟩ (both symbols denote an advanced ⟨ɰ⟩). The equivalent X-SAMPA symbols are
M\_+, respectively. Other possible transcriptions include a centralized ⟨j⟩ (⟨j̈⟩ in the IPA,
j_" in X-SAMPA), a centralized ⟨ɰ⟩ (⟨ɰ̈⟩ in the IPA,
M\_" in X-SAMPA) and a non-syllabic ⟨ɨ⟩ (⟨ɨ̯⟩ in the IPA,
1_^ in X-SAMPA).
For the reasons mentioned above and in the article velar approximant, none of those symbols are appropriate for languages such as Spanish, whose post-palatal approximant consonant (not a semivowel) appears as an allophone of /ɡ/ before front vowels and is best transcribed ⟨ʝ̞˗⟩, ⟨ʝ˕˗⟩ (both symbols denote a lowered and retracted ⟨ʝ⟩), ⟨ɣ̞˖⟩ or ⟨ɣ˕˖⟩ (both symbols denote a lowered and advanced ⟨ɣ⟩). The equivalent X-SAMPA symbols are
Especially in broad transcription, the post-palatal approximant may be transcribed as a palatalized velar approximant (⟨ɰʲ⟩, ⟨ɣ̞ʲ⟩ or ⟨ɣ˕ʲ⟩ in the IPA,
G_o_j in X-SAMPA).