1) Development 2) Evolution 
In linguistics, assibilation is the term for a sound change resulting in a sibilant consonant. It is commonly the final phase of palatalization. ==Romance languages== The word `assibilation` itself contains an example of the phenomenon, being pronounced /əsɪbɪleɪʃən/. The classical Latin tio was pronounced /tio/ (for example, assibilatio w.....
• (n.) Change of a non-sibilant letter to a sibilant, as of -tion to -shun, duke to ditch.
As·sib`i·la'tion noun Change of a non- sibilant letter to a sibilant, as of - tion to - shun , duke to ditch . 
[n] - the development of a consonant phoneme into a sibilant
noun the development of a consonant phoneme into a sibilant