Phonetics
Many of the characteristic features of Mishnaic Hebrew pronunciation may well have been found already in the period of Late Biblical Hebrew. A notable characteristic distinguishing it from Biblical Hebrew of the classical period is the spirantization of post-vocalic stops (b, g, d, p, t, k), which it has in common with Aramaic.
A new characteristic is that final /m/ is often replaced with final /n/ in the Mishna (see Bava Kama 1:4, "מועדין"), but only in agreement morphemes. Perhaps the final nasal consonant in these morphemes was not pronounced, and instead the vowel previous to it was nasalized. Alternatively, the agreement morphemes may have changed under the influence of Aramaic.
Also, some surviving manuscripts of the Mishna confuse guttural consonants, especially (א) (a glottal stop) and 'ayin (ע) (a voiced pharyngeal fricative). That could be a sign that they were pronounced the same in Mishnaic Hebrew.
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