|IPA||[a] or [ä]|
Qamatz (Hebrew: קָמַץ, IPA: [kaˈmats]) is a Hebrew niqqud (vowel) sign represented by two perpendicular lines (looking like an uppercase T) ⟨ ָ ⟩ underneath a letter. In modern Hebrew (Sephardi/Israeli), it usually indicates the phoneme /a/ which is close to the "a" sound in the English word far and is transliterated as a and thus its sound is identical to the sound of pataḥ in modern Hebrew. In some cases it indicates the phoneme /o/, equal to the sound of ḥolam.
Qamatz Qaṭan, Qamatz Gadol, Ḥataf Qamatz 
Qamatz Qaṭan vs. Qamatz Gadol 
The Hebrew of the late centuries BC and early centuries AD had a system with five phonemic long vowels [aː eː iː oː uː] and five short vowels [a e i o u]. In the later dialects of the first millennium AD, phonemic vowel length disappeared, and instead was automatically determined by the context, with vowels pronounced long in open syllables and short in closed syllables. However, the previous vowel phonemes merged in various ways that differed from dialect to dialect. In Tiberian Hebrew, which underlies the written system of vowels, short [a] became /a/ (indicated by pataḥ ); long [oː] became /o/ (indicated by ḥolam); while [aː] and [o] both merged into an in-between sound /ɔ/ (similar to the vowel in English "caught"), which was indicated by qamatz. In the Babylonian Hebrew dialect, however, short and long variants simply merged, with [a] and [aː] becoming /a/, while [o] and [oː] became /o/; and this system underlies the pronunciation of Modern Hebrew.
The result is that the vowel written with qamatz might be pronounced as either /a/ or /o/, depending on historical origin. It is often said that the two sounds can be distinguished by context:
- The qamatz sound of [o], known as Qamatz Qaṭan (Hebrew: קָמַץ קָטָן, IPA: [kaˈmats kaˈtan], "small qamatz") occurs in a "closed syllable", i.e. one which ends in a consonant marked with a shwa nakh (zero vowel) or with a dagesh ḥazaq (which indicates that the consonant was pronounced geminated, i.e. doubled);
- The qamatz sound of [a], known as Qamatz Gadol (Hebrew: קָמַץ גדול, IPA: [kaˈmats gaˈdol], "big qamatz") occurs in an "open syllable", i.e. any other circumstance: one which ends in a consonant followed by a normal vowel, a consonant at the end of a word and with no vowel marking, or a consonant marked with a shwa na (originally pronounced [ǝ].
Unfortunately, the two varieties of shwa are written identically, and pronounced identically in Modern Hebrew; as a result, there is no reliable way to distinguish the two varieties of qamatz when followed by a vowel marked with a shwa. (In some cases, Biblical texts are marked with a metheg or other cantillation mark that helps to indicate which pronunciation is intended, but this usage is not consistent, and in any case such marks are absent in non-Biblical texts.)
An example of the qamatz qatan is the Modern Hebrew word תָּכְנִית ([ˈtoχnit], "program").
According to the standard Hebrew spelling rules as published by The Academy of the Hebrew Language, words which have a qamatz qatan in their base form must be written without a vav, hence the standard vowel-less spelling of תָּכְנִית is תכנית. In practice, however, Modern Hebrew words containing a qamatz qatan do add a vav ⟨ו⟩ to indicate the [o] pronunciation; hence the "nonstandard" spelling תוכנית is common in newspapers and is even used in several dictionaries, for example Rav Milim. Words, which in their base form have a ḥolam that changes to qamatz qaṭan in declination, retain the vav in vowel-less spelling: the noun חֹפֶשׁ ([ˈχofeʃ], "freedom") is spelled חופש in vowel-less texts; the adjective חָפְשִׁי ([χofˈʃi], "free") is spelled חופשי in vowel-less text, despite the use of qamatz qatan, both according to the standard spelling and in common practice.
Some books print the qamatz qaṭan differently, although it is not consistent. For example, in siddur Rinat Yisrael the vertical line of qamatz qatan is longer. In a book of Psalms used by some Breslov hassidim the qamatz qatan is bolder. In the popular niqqud textbook Niqqud halakha le-maase by Nisan Netser, the qamatz qatan is printed as an encircled qamatz for didactic purposes.
Unicode defines the code point U+05C7 QAMATS QATAN, although the appearance of the character in the code chart is identical to that of U+05B8 QAMATS and its usage is not required.
Ḥaṭaf Qamatz 
Ḥaṭaf Qamatz (Hebrew: חֲטַף קָמָץ, IPA: [χaˈtaf kaˈmats]) is a "reduced qamatz". Like qamatz qatan, it is pronounced [o], but the rationale for its usage is different: it replaces the shva on letters which require a shva according to the grammar, but where the traditional pronunciation is o̞. This mostly happens with gutturals, for example in אֳרָנִים ([oʁaˈnim], "pines", the plural form of Hebrew pronunciation: [oraˈnim], [ˈoʁen]), but occasionally also on other letters, for example שֳׁרָשִׁים ([ʃoʁaˈʃim], "roots", the plural of שֹׁרֶשׁ [ˈʃoʁeʃ]) and צִפֳּרִים ([tsipoˈʁim], "birds", the plural of [tsiˈpoʁ]).
Pronunciation and transliteration 
The following table contains the pronunciation and transliteration of the different qamatzes in reconstructed historical forms and dialects using the International Phonetic Alphabet. The transcription in IPA is above and the transliteration is below.
|בָ||Qamatz Gadol||Big Qamatz||[a]||ô||[aː]||[o]||[ɔː]||?||?|
|בָה, בָא||Qamatz Male||Full Qamatz||[a]||ô||[aː]||[o]||[ɔː]||?||?|
|בָ||Qamatz Qatan||Small Qamatz||[o]||ô||[o]||[o]||[ɔ]||?||?|
|חֳ||Hataf Qamatz||Reduced Qamatz||[o]||ô||[o]||[o]||[ɔ̆]||?||?|
Vowel Length comparison 
These vowel lengths are not manifested in Modern Hebrew. The short o (Qamatz Qaṭan) and long a (Qamatz) have the same niqqud. Because of this, the short o (Qamatz Qaṭan) is usually promoted to a long o (ḥolam male) in Israeli writing, written as a vav ⟨ו⟩, for the sake of disambiguation.
By adding two vertical dots (shva) the vowel is made very short.
|Vowel comparison table|
|Ḥolam||Qamatz Qaṭan||Reduced Qamatz|
Unicode encoding 
Note: the glyph for QAMATS QATAN may appear empty or incorrect if one applies a font that cannot handle the glyph necessary to represent Unicode character U+05C7. Usually this Unicode character isn't used and is substituted with the similar looking QAMATS (U+05B8).
See also