For example, the alveolo-palatal consonants [ɕ ʑ] are sometimes characterized as a distinct primary articulation and sometimes as palatalization of postalveolar fricatives, equivalent to [ʃʲ ʒʲ] or [s̠ʲ z̠ʲ].
In the official IPA there remains only an alternative symbol for velarization/pharyngealizaton that is superposed over the primary (e.g. ⟨ɫ⟩ for dark L), but that has font support for a limited number of consonants and is inadvisable for others, where it can be illegible.
Superscripts are also used iconically to indicate the onset or release of a consonant, the on-glide or off-glide of a vowel, and fleeting or weak segments.
Among other things, these phenomena include pre-nasalization ([ᵐb]), pre-stopping ([ᵖm, ᵗs]), affrication ([tᶴ]), pre-affrication ([ˣk]), trilled, fricative, nasal, and lateral release ([tʳ, tᶿ, dⁿ, dˡ]), rhoticization ([ɑʵ]), and diphthongs ([aᶷ]).
The 2015 edition of the Extensions to the International Phonetic Alphabet formally advocates superscript letters for the first time since 1989, specifically for the release of plosives.