The Hebrew word for "alphabet" is אלף-בית (alef-bet), named after the first two letters of the Hebrew alphabet. The Hebrew alphabet was in origin an abjad, in other words it had letters for consonants only, but means were later devised to indicate vowels, first by using consonant letters as matres lectionis, later by separate vowel points or niqqud.
The modern script used for writing Hebrew (usually called the Jewish script by scholars, and also traditionally known as the square script, or the Assyrian script), evolved during the 3rd century BC from the Aramaic script, which was used by Jews for writing Hebrew since the 6th century BC. Prior to that, Hebrew was written using the old Hebrew script, which evolved during the 9th century BC from the Phoenician script; the Samaritans still write Hebrew in a variant of this script for religious works (see Samaritan alphabet).
Both the old Hebrew script and the modern Jewish script have only one case, but in the modern script some letters have special final forms used only at the end of a word. This is similar to the Arabic alphabet, although much simpler. The Hebrew alphabet is an abjad: vowels are normally not indicated. Where they are it is because a weak consonant such as א alef, ה he, ו vav, or י yod has combined with a previous vowel and become silent or by imitation of such cases in spelling of other forms.
To preserve the proper vowel sounds, scholars developed several different sets of diacritic symbols called niqqud (ניקוד; literally: "applying points"). One of these, the Tiberian system, eventually prevailed. Aaron ben Moses ben Asher, and his family for several generations, are credited for creating and maintaining the system. These points are normally used only for special purposes, such as Biblical books intended for study, in poetry, or when teaching the language to children. The Tiberian system also includes a set of cantillation marks used to indicate how scriptural passages should be chanted, and decorative "crowns" used only for Torah scrolls.
The following table is a breakdown of each letter in the Hebrew alphabet, describing its written glyph or glyphs, its name or names, its Latin scripttransliteration values used in academic work, and its pronunciation in reconstructed historical forms and dialects using the International Phonetic Alphabet. If two glyphs are shown for a letter, then the left-most glyph is the Final form of the letter (or right-most glyph if your browser doesn't support right-to-left text layout).
Historically, the consonants ב bet, ג gimel, ד dalet, כ kaf, פ pe, and ת tav each had two sounds: one hard (plosive consonant), and one soft (fricative consonant), depending on the position of the letter and other factors. When vowel diacritics are used, the hard sounds are indicated by a central dot called dagesh (דגש), while the soft sounds lack a dagesh. In masoretic manuscripts, the soft fricative consonants are indicated by a small line on top of the letter; this diacritical mark is called raphe (רפה), but its use has been largely discontinued in printed texts.
א alef, ה he, ו vav and י yod are consonants that can sometimes fill the position of a vowel. vav and yod in particular are more often vowels than they are consonants.
ש shin and sin are two separate phonemes written with the same letter. They are not mutually allophonic. When vowel diacritics are used, the two phonemes are differentiated with a shin-dot or sin-dot; the shin-dot is above the upper-right side of the letter, and sin-dot is above the upper-left side of the letter.
In Israel's general population, many consonants have merged to the same pronunciation. They are:
א alef with ayin and (varyingly) ה he
ב bet (without dagesh) with ו vav
ח het with כ kaf (without dagesh)
ט tet with ת tav (both with and without dagesh)
כ kaf (with dagesh) with ק qof
ס samekh with שׂ sin (but not with שׁ shin)
צ tsadi with the consonant cluster תס tav-samekh
Some of the letters, as well as their consonantal function, also acted as matres lectionis to represent vowels, as follows:
ê, ệ, ậ, â, ô
ê, ệ, ậ, â, ô
î, ê, ệ
Some of the variations in sound mentioned above are due to a systematic feature of Ancient Hebrew. The six consonants /p t k b d g/ were pronounced differently depending on their position. These letters were also called BeGeDKePHaT (pronounced/beɪgɛd'kɛfɛt/) letters. (The full details are very complex; this summary omits some points.) They were pronounced as stops [p t k b d g] at the beginning of a syllable, or when doubled. They were pronounced as fricatives[p̄ ṯ ḵ ḇ ḏ ḡ] — IPA[f θ x v ð ɣ] when preceded by a vowel. The stop and double pronunciations were indicated by the dagesh. In Modern Hebrew the sounds [ḏ] and [ḡ] have reverted to [d] and [g], and [ṯ] has become [t], so only the remaining three letters show variation.
ו vav was a semivowel /w/ (as in English, not as in German).
שׂ sin (the /s/ variant of ש shin) was originally different from both שׁ shin and ס samekh, but had become /s/ the same as ס samekh by the time the vowel pointing was devised. Because of cognates with other Semitic languages, this phoneme is known to have originally been a lateral consonant, most likely IPA the fricative/ɬ/ (as in Welsh /ll/) or the affricate/tɬ/ (as in Náhuatl /tl/).
Following the Babylonian exile, Jews gradually stopped using the Hebrew script, and instead adopted the BabylonianAramaic script (which was also originally derived from the Phoenician script). This script, used for writing Hebrew, later evolved into the Jewish, or "square" script, that is still used today. "Square"-related scripts were in use all over the Middle East for several hundred years, but following the rise of Christianity (and later, the rise of Islam), they gave way to the Roman and Arabic alphabets, respectively. According to traditional Jewish thought, the Hebrew writing system contained all the current letters at the time of Moses, although Ezra is known for his contribution to the square form.
Following the decline of Hebrew and Aramaic as the spoken languages of the Jews, the Hebrew alphabet was adopted in order to write down the languages of the Jewish diaspora (Karaim, Judæo-Arabic, Ladino, Yiddish, etc.). The Hebrew alphabet was retained as the alphabet used for writing down the Hebrew language during its rebirth in the end of the 19th century, despite several unsuccessful attempts to replace it with the Latin alphabet.