Another series of changes was the frication of voiced stops, which is widely attested in Egyptian Greek starting from the 1st century AD, but may have been generalized at a later date, possibly in the late Roman or early Byzantine period.
Yet another series of changes was the frication of aspirated voiceless stops, which is attested in several locations from the 1st century AD, but seems to have been generalized at a later date, possibly in the late Roman or early Byzantine period.
The primary point of contention comes from the diversity of the Greek-speaking world: evidence suggests that phonological changes occurred at different times according to location or speaker background.
A first explanation would be dialectal differences (influence of foreign phonological systems through non-native speakers); changes would then have happened in Egyptian Greek before they were generalized in Attic.
[10] ....Διουκλεῖς κὴ Κωτίλα ἀντίθεντι τὰν ϝιδίαν θρεπτάν, ἧ ὄνιουμα Ζωπουρίνα, ἱαρ[ὰν] τεῖ Σεράπει, παραμείνασαν αὐτεῖς ἇς κα ζῶνθι ἀνενκλείτως, τὰν ἀνάθεσιν ποιούμενει διὰ τῶ σ[ο]υνεδρίω κατὰ τὸν νόμον.Greek pronunciation: [...diuklêːs kɛː koːtílaː antítʰenti taːn widíaːn tʰreptán, hɛː ónjuma zoːpuríːnaː, hiaràn teː serápeː, paraméːnaːsan auteːs hâs kaː zôːntʰi aneŋkléːtoːs, taːn anátʰesin pojúːmeneː dia toː sunhedríoː kata ton nómon.
For example, well into the Roman period, there is indication from musical inscriptions and grammarians such as Velius Longus and Philostratus of the preservation of vowel length and pitch accent.
[13] A monophthongal pronunciation of υι as /yː/ is written in parentheses as a dialectal trait of Great Attic[clarify] beginning in the late classical period.
What exact sound ῥ represented is a matter of discussion, but it should probably be regarded as an allophone of the /r/ notated by ρ. ζ denotes a /zz/ geminate between vowels.
περὶ ὧν Θισ[β]εῖς λόγους ἐποιήσαντο· περὶ τῶν καθ᾿αὑ[τ]οὺς πραγμάτων, οἵτινες ἐν τῆι φιλίαι τῆι ἡμετέραι ἐνέμειναν, ὅπως αὐτοῖς δοθῶσιν [ο]ἷς τὰ καθ᾿ αὑτοὺς πράγματα ἐξηγήσωνται, περὶ τούτου τοῦ πράγματος οὕτως ἔδοξεν· ὅπως Κόιντος Μαίνιος στρατηγὸς τῶν ἐκ τῆς συνκλήτου [π]έντε ἀποτάξηι οἳ ἂν αὐτῶι ἐκ τῶν δημοσίων πρα[γμ]άτων καὶ τῆς ἰδίας πίστεως φαίνωνται.Greek pronunciation: [peri hoːn tʰizbîːs lóɡuːs epojéːsanto; peri toːn katʰ hautûːs praːɡmátoːn, hoítines en tiː pʰilíaːi tiː heːmetéraːi enémiːnan, hópoːs autois dotʰôːsin hois ta katʰ hautùːs práːɡmata ekseːɡéːsoːntai, peri túːtuː tuː práːɡmatos húːtoːs édoksen; hópoːs ˈkʷintos ˈmainios strateːɡòs toːn ek teːs syŋkléːtuː pénte apotáksiː, hoi an autoːi ek toːn deːmosíoːn praːɡmátoːn kai teːs idíaːs písteoːs pʰaínoːntai.
The following late Ptolemaic Egyptian papyrus from 154 BC is rendered in popular pronunciation including the loss of vowel length distinction and shift to a stress accent.
The interchange of ι for η and υ suggests an early raising to /i/ for the former and loss of lip-rounding for the latter; this occurs only in highly restricted phonetic conditions (i.e. in labial environments),[27] or may be an isolated dialectal trait.
In the Roman period the αυ and ευ diphthongs developed narrower articulations, possibly closing to [aɸʷ, aβʷ], [eɸʷ, eβʷ] or even, depending on when lip-rounding was lost, [aɸ, aβ] and [eɸ, eβ].
[32] Despite the lack of clear evidence for the fricativization of aspirated plosives in the Koine, φ, θ, and χ perhaps started to become fricatives in areas outside Egypt such as the northern Mediterranean.
[36] Also, there is frequent post-nasal voicing of voiceless stops, which is strengthened in Egypt because of Coptic influence but was eventually standardized everywhere and is a rule in Modern Greek.
εὖ οὖν πυήσας κομισάμενός μου τὴν ἐπιστολὴν πέμσις μυ Πίνδαρον εἰς τὴν πόλιν τὸν πεδιοφύλακα τῆς Διονυσιάδος, ἐπὶ ἐρώτησέ με Ἑρμοναξ εἵνα αὐτὸν λάβῃ εἰς Κερκεσοῦχα καταμαθῖν τὸν ἐλαιῶνα αὐτοῦ, ἐπὶ πυκνός ἐστιν και θέλι ἐξ αὐτὸν ἐκκόψαι φυτά, εἵνα ἐνπίρος κοπῇ τὰ μέλλοντα ἐκκόπτεσθαι.Greek pronunciation: [ˈlucios beˈle̝nos ˈɟemelos saˈbino to hyˈjo ˈcʰerin.
ev un pyˈe̝sas komiˈsameˈnoz mu te̝n epistoˈle̝(n) ˈpem(p)siz my ˈpindaron is te̝m ˈbolin tom bedioˈpʰylaka tiz djonyˈsjados, eˈpi eˈrote̝ˈse me erˈmonaks in(a) a(f)ton ˈlavi is cerceˈsukʰa katamaˈtʰi(n) ton eleˈon(a) a(f)tu, eˈpi pyˈknos estin ce ˈtʰeli eks afˈton eˈkopse pʰyˈta, ina emˈbiros koˈpi ta ˈmelonda eˈkoptestʰe.
πρὼ [μ]ὲν πάντων εὔχωμαι τῷ κυρίῳ θεῷ περὶ τῆς σῆς ὡλοκληρίας ὅπως ὑιένοντα σοὶ καὶ εὐθυμοῦντι ἀπωλάβῃς τὰ παρ' ἐμοῦ γράμματα.
pro men ˈpandon ˈefxome to cyˈrio θeˈο peri tis sis olokliˈrias opos yˈʝenonda sy ce efθiˈmundi apoˈlavis ta par emu ˈɣramata.
Get from him out of my pay one and a half (talents)...The ancient distinction between long and short vowels was lost in popular speech at the beginning of the Koine period.
"By the mid-second century [BCE] however, the majority system had undergone important changes, most notably monophthongization, the loss of distinctive length, and the shift to a primary stress accent.
"[45] From the 2nd century BC, spelling errors in non-literary Egyptian papyri suggest stress accent and loss of vowel length distinction.
The widespread confusion between ο and ω in Attic inscriptions starting in the 2nd century AD was probably caused by a loss of vowel length distinction.
[50] One theory to explain this difference is that pre-vocalic ει may have kept a diphthongal value [ej] until the 4th century BC, the [j] being progressively perceived as a glide from /e/ to the next vowel.
[66] Allen also believes that the fricative pronunciation was not generalized at once; for instance, Jewish catacombs inscriptions still show a diphthongal value in the 2nd–3rd century AD.
)[81][82] Transcriptions into Gothic and, to some extent, Armenian suggest that υ still retained a /y/ pronunciation, and the transition to /i/ in mainstream Greek is thought to have taken place at the end of the 1st millennium.
[86] Among consonants, β, δ, γ ζ, φ, θ and χ all shifted over the course of the Koine period, but there is disagreement regarding timing of sound changes, and likely varied by dialect.
[89] Horrocks agrees with Gignac on finding evidence that geminate consonants tended to simplify beginning from the 3rd century BC, as seen in their arbitrary use in less literate writing.
[115] Georgian loans in the 9th and 10th centuries similarly show inconsistency in transcribing β and γ as a stop or fricative; β is consistently rendered as ბ b rather than ვ v, while γ may be written with an adapted symbol ღ for fricative /ɣ/ or with ჟ [ʒ] (approximating [ʝ] in palatal position), but also with stop გ g.[116] There is probable evidence for a peculiarly early shift of /d/ > /ð/ in 6th century BC Elean, seen in the writing of ζ for δ.
[119] The weakness of final ν /n/, frequently before a stop consonant, is attested in Egypt in both Hellenistic and Roman times, seen directly in graphic omission and hypercorrect insertion, though its complete loss would not be carried through until the medieval period and excluding the South-Italian, south-eastern and Asia Minor dialects.
[120] The development of voiced allophones [b], [d], [ɡ] of voiceless stops π, τ, and κ after nasals is also evidenced in Pamphylia as early as the 4th century BC and in the Egyptian papyri (mostly Roman period) in the interchange with β, δ, and γ in post-nasal positions (where these letters retained their ancient plosive values, as noted above.