In linguistics, an elision or deletion is the omission of one or more sounds (such as a vowel, a consonant, or a whole syllable) in a word or phrase. However, these terms are also used to refer more narrowly to cases where two words are run together by the omission of a final sound. An example is the elision of word-final /t/ in English if it is preceded and followed by a consonant: "first light" is often pronounced /fɜ:s laɪt/. Many other terms are used to refer to particular cases where sounds are omitted. Citation forms and contextual forms A word may be spoken individually in what is called the citation form. This corresponds to the pronunciation given in a dictionary. However, when words are spoken in context, it often happens that some sounds that belong to the citation form are omitted. Elision is not an all-or-nothing process: elision is more likely to occur in some styles of speaking and less likely in others. Many writers have described the styles of speech in which elision is most commonly found, using terms such as "casual speech", "spontaneous speech", "allegro speech" or "rapid speech". In addition, what may appear to be the disappearance of a sound may in fact be a change in the articulation of a sound that makes it less audible. For example, it has been said that in some dialects of Spanish the word-final -ado, as in cansado (tired) is pronounced /ado/ in citation form but the /d/ is omitted in normal speech, giving "cansao". More careful description will show that the Spanish phoneme /d/ is usually pronounced as a voiced dental fricative [ð] when it occurs between vowels. In casual speech it is frequently weakened to a voiced dental approximant [ð̞]. The most extreme possibility is complete elision resulting in a diphthong with no observable consonantal tongue gesture. In this view, elision is the final stage in lenition or consonant weakening, the last phase of a cline or continuum describable as d > ð > ð̞ > ∅. Whether the elision is of vowel or consonant, if it is consistent through time, the form with elision may come to be accepted as the norm: tabula > tabla as in Spanish, mutare > muer ("change, molt") in French, luna > lua ("moon") in Portuguese. It is usual to explain elision and related connected-speech phenomena in terms of the principle