Pataḥ (Hebrew: פַּתַח pataḥ, IPA: [paˈtaχ], Biblical: paṯaḥ ) is a Hebrew niqqud vowel sign represented by a horizontal line ⟨ ַ ⟩ underneath a letter. In modern Hebrew, it indicates the phoneme /a/ which is close to the "a" sound in the English word far and is transliterated as an a.
In Modern Hebrew, a pataḥ makes the same sound as a qamatz, as does the ḥaṭaf pataḥ (Hebrew: חֲטַף פַּתַח IPA: [χaˈtaf paˈtaχ], "reduced pataḥ"). The reduced (or ḥaṭaf) niqqud exist for pataḥ, qamatz, and segol which contain a shva next to it.
The following table contains the pronunciation and transliteration of the different pataḥs in reconstructed historical forms and dialects using the International Phonetic Alphabet. The pronunciation in IPA is above and the transliteration is below.
The letters Bet ⟨ב⟩ and Het ⟨ח⟩ used in this table are only for demonstration. Any letter can be used.
A pataḥ on a letter ח at the end of a word is sounded before the letter, and not behind. Thus, נֹחַ (Noah; properly transliterated as Noaḥ ) is pronounced /no.aχ/ in Modern Hebrew and /no.aħ/ in Biblical Hebrew. This only occurs at the ends of words and only with pataḥ and ח, ע, and הּ (that is, ה with a dot (mappiq) in it). This is sometimes called a pataḥ gnuva, or "stolen" pataḥ (more formally, "furtive pataḥ"), since the sound "steals" an imaginary epenthetic consonant to make the extra syllable.
In addition, a letter with a pataḥ or qamatz with a succeeding, articulated yud ⟨י⟩ makes the diphthong /ai̯/, similar to the diphthong in the English words fine and why.
Vowel Length comparison 
By adding two vertical dots (shva) the vowel is made very short. However, these vowels lengths are not manifested in Modern Hebrew.
Unicode encoding 
See also