Ts–ch merger

In phonology, the ts–ch merger is the merger of the voiceless alveolar affricate and the voiceless postalveolar affricate.
In Russian, it is the merger of the consonants rendered by letters Che and Tse. If the shift is towards Tse, it is called tsokanye ; the shift towards Che is called chokanye. Both pronunciation features are found in some Northern Russian dialects.
It is a regular sound change of Lower Sorbian, but not Upper Sorbian, as seen in the difference between Lower Sorbian wikt:cas#Lower Sorbian and Upper Sorbian wikt:čas#Upper Sorbian, both meaning "time".
In Polish the merger is part of a more general dialectal feature called mazurzenie, present in many Polish dialects but named after the Masovian dialect.
It also occurs in a few areas of the Chakavian dialect of Serbo-Croatian, known as tsakavism.
The sabesdiker losn feature of Northeastern Yiddish includes the merger.
Greek-speaking people may merge into when speaking foreign languages that contain those sounds.