From Proto-Slavic *orz-.

раз- • (raz-)

1. Inseparable verbal prefix that denotes distribution, destruction, breaking into pieces, undoing or removing.; de-, dis-, un-

• зар (zar)

• рас- (ras-) (before voiceless consonants)

From Proto-Slavic *orz-.

раз- • (raz-)

1. (used with verbs) dis-, un-

   ‎раз- (raz-) + ‎-ити (-iti, “to go”) + ‎сѧ (sę) → ‎разити сѧ (raziti sę, “to go asunder, to disagree”)

• развѣ (razvě)
• разьнъ (razĭnŭ)

• разо- (razo-) — before certain consonant clusters
• рас- (ras-) — before voiceless consonants

Inherited from Old East Slavic роз- (roz-), from Proto-Slavic *orz-. The spelling "раз-" was reinforced by Old Church Slavonic раз- (raz-), as well as vowel reduction, which is also reflected in Belarusian раз- (raz-).

• IPA^(key): [rəz]

раз- • (raz-)

1. (used with verbs) asunder, apart
2. (used with verbs) dis-, di-, un-

   ‎разо- (razo-) + ‎-йти́ (-jtí, “to go”) + ‎-сь (-sʹ) → ‎разойти́сь (razojtísʹ, “to go asunder, to disagree”)

   ‎раз- (raz-) + ‎дева́ть (devátʹ, “to put”) → ‎раздева́ть (razdevátʹ, “to undress”)

3. (used with verbs) enlarged action

   ‎раз- (raz-) + ‎рабо́тать (rabótatʹ, “to work”) → ‎разрабо́тать (razrabótatʹ, “to develop, to work out”)

4. (used with verbs) with reflexives, giving free rein to

   ‎раз- (raz-) + ‎говори́ть (govorítʹ, “to talk”) + ‎-ся (-sja) → ‎разговори́ться (razgovorítʹsja, “to talk up a storm”)

5. (used with verbs, in the negative) not quite

   ‎не (ne, “not”) + ‎рас- (ras-) + ‎слы́шать (slýšatʹ, “to hear”) → ‎не расслы́шать (ne rasslýšatʹ, “to not quite hear”)

When stressed, раз- (raz-) normally changes into ро́з- (róz-), and the voiceless variant рас- (ras-) correspondingly becomes ро́с- (rós-):

• разда́ть (razdátʹ, “to distribute”) → past passive participle ро́зданный (rózdannyj)
• расписа́ть (raspisátʹ, “to paint, to decorate”) + -ь (-ʹ, noun-forming suffix, which normally causes stress to move onto a prefix) → ро́спись (róspisʹ, “painting, mural”)

• Vasmer, Max (1964–1973) “раз-”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress

Inherited from Proto-Slavic *orz-.

ра̀з- (Latin spelling ràz-)

1. Inseparable verbal prefix that denotes distribution, destruction, breaking into pieces, undoing or removing.; de-, dis-, un-

• зар