The second may be the result of the first, but they often differ. A vowel may "palatalize" a consonant (sense 1), but the result might not be a palatalized consonant in the phonetic sense (sense 2), or the phonetically palatalized (sense 2) consonant may occur irrespective of front vowels.
Conversely, the word "palatalization" may also be used for the effect a palatal or palatalized consonant exerts on nearby sounds, as in the Finno-Ugric language Erzya, where the front vowel [æ] only occurs as an allophone of [a] after a palatalized consonant, as seen in the pronunciation of the name of the language itself, [erzʲæ]. However, while the process may be called palatalization, the resulting vowel [æ] is not called a palatalized vowel in the phonetic sense. Terminology such as "palatal vowel" is found, however, but this is primary and not secondary articulation.
"Pure" palatalization is denoted by a small superscript in IPA. This is a modification to the articulation of a consonant, where the middle of the tongue is raised, and nothing else. It may produce a laminal articulation of otherwise apical consonants such as /t/ and /s/. It is a phonemic feature in some languages; a common misconception is that it's merely allophonic, like in English. Phonemic palatalization is contrasted with either plain or velarized articulation. In Baltic-Finnic languages, Baltic and Slavic languages, the contrast is with plain consonants, but in Irish, it is with velarized consonants.
Phonetically palatalized consonants may vary in their exact realization. Some, but not all languages add offglides or onglides. In Russian, both plain and palatalized consonant phonemes are found in words like пальто [pʌˈlʲto], царь [tsarʲ] and Катя [ˈkatʲə]. Typically, the vowel following a palatalized consonant has a palatal offglide. In Hupa, on the other hand, the palatalization is heard as both an onglide and an offglide: [aʲkʲa].
Palatalization can also occur as a suprasegmental feature that affects the pronunciation of an entire syllable. This is the case in Skolt Sami, a language which is unusual in contrasting suprasegmental palatalization with segmental palatalization (i.e., inherently palatalized consonants).
Palatalization may be a synchronic phonological process, i.e., some phonemes are palatalized in certain contexts, typically before front vowels or especially high front vowels, and remain non-palatalized elsewhere. This is usually phonetic palatalization, as described above, but need not to be. It is usually allophonic and it may go unnoticed by native speakers. As an example, compare the /k/ of English key with the /k/ of coo, or the /t/ of tea with the /t/ of took. The first word of each pair is palatalized, but few English speakers would perceive them as distinct.
The variation might be seen as allophonic variation as long as the "palatal" sound causing the palatalization is there. However, syncope or elision might delete this sound, and thus only the palatalization remains as a distinct feature. This process is widespread in Baltic-Finnic languages, which have lost their original (Uralic) phonemic palatalization but some have regained it. For a minimal pair, consider Estonian kass [kɑsʲ:] from *kassi "cat" vs. kas [kɑs:] (interrogative).
Sometimes palatalization is part of a synchronic grammatical process, such as palatalizing the first consonant of a verb root to signal the past tense. This type of palatalization is phonemic, and is recognized by the speakers as a contrasting feature. However, what may have started off as phonetic palatalization can quickly evolve into something else, so not all of the resulting consonants are necessarily palatalized phonetically.
Palatalization may be a diachronic phonemic split, that is, a historical change by which a phoneme becomes two new phonemes over time through phonetic palatalization. Old historical splits have frequently drifted since the time they occurred, and may be independent of current phonetic palatalization. For example, Votic has undergone such a change historically, in for example keeli → tšeeli ('language'), but there is currently an additional distinction between palatalized laminal and non-palatalized apical consonants.
While the great majority of palatalization effects are connected with sequences with a consonant adjacent to a high front or mid front vowel or glide, palatalization may occur spontaneously in a sense. In Southwestern Romance, l in word-initial clusters after a voiceless obstruent became palatalized, as Latin clamare ('to call') → Italian chiamare /kjamare/, Old Portuguese chamar, while in Spanish the obstruent drops before the palatalized liquid: llamar /ʎamar/. Differently, in an even larger area, Latin *[kt] became *[kʲt] (or even *[kʲtʲ]) thus from a form like Latin octō ('eight') French huit, Spanish ocho, Portuguese oito /oitu/. It is entirely possible that Italian otto also continues Proto-Romance *[okʲtu] rather than being a straight shot from [oktu].
Palatalization is usually triggered only by non-open front vowels; but counterexamples to this are also found. Certain dialects of American English that have a front [æ] in words like car and garden (most notably, those participating in the Northern Cities Vowel Shift) may pronounce them with a noticeable palatal offglide: [kʲæɹ], [ˈgʲæɾɪn] and the like for car, garden. In Gallo-Romance, *[ka] became *[tʃa] very early, with the subsequent loss of the *t and some further developments of the vowel, thus *cattus ('cat') → chat /ʃa/, calvus ('bald') → chauve /ʃov/, *blanca ('white' fem.) → blanche /blɑ̃ʃ/, catena ('chain') → chaine /ʃɛn/, carus ('dear') → cher /ʃɛʀ/, and so on. Early English borrowings from French show the original affricate, as chamber ('[private] room') < Old French chambre < camera; cf French chambre /ʃɑ̃bʀ/ ('room')
Palatalization has played a major role in the history of the Uralic, Romance, Slavic, Korean, Japanese, Chinese, Twi etc, and Indic languages, among many others throughout the world. In Japanese, for example, allophonic palatalization affected the alveolar stops /t/ and /d/, turning them into alveolo-palatal affricates [tɕ] and [dʑ] before /i/. Japanese has only recently regained phonetic [ti] and [di] through borrowed words, and thus this originally allophonic palatalization has become lexical. Similar change has also happened in Polish.
Such phonemic splits due to historic palatalization are common in many other languages. Some English examples of cognate words distinguished by historical palatalization are church vs. kirk, witch vs. wicca, ditch vs. dike, and shirt vs. skirt. In witch/wicca the latter form is a spelling pronunciation based on unfamiliarity with Old English spelling conventions (wicca was presumably [ˈwɪʧːa] < *wikjā ); in the other cases the words come from related dialects or languages (skirt from Danish) which differed in the place and degree of palatalization. More recently, the original /t/ of question and nature have come to be pronounced as [ʧ] before [j] in some English dialects, and similarly the original /d/ of soldier and procedure have come to be pronounced as [ʤ]. This effect can also be seen in casual speech in some dialects, where Do you want to go? comes out as , and Did you eat yet? as .
There are various other local or historical uses of the word. In Slavic linguistics, the "palatal" fricatives marked by a háček are really postalveolar consonants that arose from palatalization historically. There are also phonetically palatalized consonants (marked with an acute accent) that contrast with this; thus the distinction is made between "palatal" (postalveolar) and "palatalized". Such "palatalized" consonants are not always phonetically palatalized; e.g. in Russian, when /t/ undergoes a so-called "palatalization", a palatalized sibilant offglide is actually added, as in тема [ˈtʲsʲɛmə].
In Uralic linguistics, "palatalization" has the standard phonetic meaning. /s/, /sʲ/, /ʃ/, /t/, /tʲ/, /tʃ/ are distinct phonemes, as they are in the Slavic languages, but /ʃ/ and /tʃ/ are not considered either palatal or palatalized sounds. Also, the Uralic palatalized /tʲ/ is a stop with no frication, unlike in Russian.
In using the Latin alphabet for Uralic languages, palatalization is typically denoted with an acute accent, as in Võro <ś>; an apostrophe, as in Karelian
; or digraphs in j, as in the Savo dialect of Finnish,