YIVO, (Yiddish: ייִוואָ), established in 1925 in Wilno, Poland (now Vilnius, Lithuania) as the Yidisher Visnshaftlekher Institut (Yiddish: ייִדישער װיסנשאַפֿטלעכער אינסטיטוט), or Jewish Scientific Institute (ייִדישער yidisher = Jewish or Yiddish, depending on the context), is a source for orthography, lexicography, and other studies related to the Yiddish language. Though it was later renamed the Institute for Jewish Research, it is almost always known by its original initials, which, in Yiddish, form the acronym "ייווא", transliterated as "YIVO".
The phoneme /v/ is represented by two letters: vet (ב, unemphasized bet) and vav (ו). Although modern Hebrew pronunciation does not differentiate between the two, the latter is historically weaker due to its being a semi-vowel (/w/).
The phoneme /k/ is represented by two letters: kaf (כ) and quf (ק). Although modern Israeli Hebrew pronunciation doesn't differentiate between the two, the latter is pronounced by some speakers as in Arabic /q/.
The phoneme /t/ is represented by two letters: tet (ט) and tav (ת). The tet was historically pronounced with pharyngealization (as in Arabic) or as an ejective (often, but misleadingly, called "emphasis"). The letter tav, when intervocalic and non-doubled (i.e. without dagesh) represented a fricative[θ]. For example, what in Modern Hebrew is /bet ˈleχem/ (or /bejt ˈleχem/) was transcribed (through Greek, which is ill-equipped to represent /ħ/) into English from Old Hebrew as "Bethleem", also demonstrating note number 5. The traditional Ashkenazi pronunciation of tau without dagesh as "s" is a continuation of this former distinction.
In old Hebrew the צ (/ʦ/) was, like ט, pharyngealized or ejective ("emphasis"). Currently, the only community of Hebrew-speakers which expresses this in speech are Yemenite Jews, whose Hebrew did not lose them, as other communities did under the influence of Yiddish and other European languages); however the emphasis led to several types of phonetic change that still exist. The exact nature of the emphatic feature is a matter of debate; the most commonly suggested possibilities are pharyngealization (as in Arabic) and glottalization (or the ejective mechanism) (as in the Ethiopian Semitic languages).
In the speech of most modern Hebrew speakers, the phoneme /χ/ is represented by two letters: het (ח) and khaf (כ). Het is presumed to historically have been a voiceless pharyngeal fricative (like Arabic ح). The voiceless pharyngeal fricative pronunciation [ħ] is found in the speech of many Teimanim, Mizrachim and Sephardim, who, like Ashkenazim, pronounce khaf as /x/.
In Biblical Hebrew, each vowel had three forms: short, long and interrupted (khataf). However, there is no audible distinction between the three in modern Israeli Hebrew, except that tsere is often pronounced /eɪ/ as in Ashkenazi Hebrew.