The most important name of God in Judaism is the Tetragrammaton, the four-letter name of God. This name is first mentioned in the book of Genesis and is usually translated as 'the Lord'. Because Jews for quite a long period of time considered it sinful to pronounce, the correct pronunciation of this name was forgotten -- the original Hebrew texts only included consonants. Modern scholars conjecture that it was pronounced "Yahweh". The Hebrew letters are named Yod-Heh-Vav-Heh, and if your browser supports a Hebrew font it is written thus: יהוה (Note that Hebrew is written from right to left, rather than left to right as in English). In English it is written as YHVH.
In appearance, YHVH is the third person singular imperfect of the verb "to be", meaning, therefore, "God is," or "God will be," or, perhaps, "God lives," the root idea of the word being, probably, "to blow," "to breathe," and hence, "to live." With this explanation agrees the meaning of the name given in Ex. iii. 14, where God is represented as speaking, and hence as using the first person — "I am". The meaning would, therefore, be "He who is self-existing, self-sufficient," or, more concretely, "He who lives," the abstract conception of pure existence being foreign to Hebrew thought.
The idea of life was intimately connected with the name YHVH from early times. God is presented as a living God, as contrasted with the lifeless gods of the heathen, and God is presented as the source and author of life (comp. I Kings xviii.; Isa. xli. 26-29, xliv. 6-20; Jer. x. 10, 14; Gen. ii. 7; etc.)
Jews also call God Adonai, or "my Lord." Since pronouncing YHVH is considered sinful, Jews would use Adonai instead in prayers. When the Masoretes[?] added vowel pointings to the text of the Tanach in the first century A.D., they gave the word YHVH the vowels of Adonai, to remind the reader to say Adonai instead. Many Christian bible translators misinterpreted this to mean that God's name was Jehovah, which is the result of combining Adonai's vowels with YHVH's consonants, written using Latin orthography in which "J" is pronounced as the English "Y." This name may be etymologically related to the Phoenician god Tammuz or Adonis.
All denominations of Judaism teach that the four letter name of God, YHVH, is forbidden to be uttered except by the High Priest, in the Temple. Since the Temple in Jerusalem is no longer extant, this name is never pronounced in religious rituals by Jews. Orthodox Jews never pronounce it for any reason. Some non-Orthodox Jews are willing to pronounce it, but for educational purposes only, and never in casual conversation or in prayer. Instead of pronouncing YHVH during prayer, Jews say "Adonai".
Jewish law requires that "fences" be built around the basic laws, so that there is no chance that the main law will ever be broken. As such, it is common Jewish practice to restrict the use of the word "Adonai" to prayer only. In conversation many Jewish people will call God "HaShem", which is Hebrew for "the Name" (this was first used in Leviticus 24:11). Many Jews also write "G-d" instead of "God". While this later substitution is by no means required by their religion (only the Hebrew name, not the English, is holy), they do it to remind themselves of the holiness attached to God's name.
A common name of God in the Hebrew Bible is Elohim.
Despite the -im ending common to many plural nouns in Hebrew, the word Elohim, when referring to God, is grammatically singular, regularly taking singular predicate forms in the Hebrew Bible. In fact, there are a few other Hebrew nouns that end in -im that are not plural, for example, mayim (water) and chayyim (life). The word elohim likely had an origin in a plural grammatical form, because, when the Hebrew Bible uses elohim not in reference to God, it takes plural forms (e.g. Ex. 20:3).
Some scholars interpret the -im ending as an expression of majesty (pluralis majestatis) or excellence (pluralis excellentiae), expressing high dignity or greatness: compare with the similar use of plurals of ba'al (master) and adon (lord). For these reasons, Christian theologians have generally pointed out that it is an exegetical fallacy to draw support for the Christian doctrine of the trinity from the apparently plural ending of the word elohim.
In Ethiopic, Amlak ("lords") is the common name for God. The singular, Eloah, is comparatively rare, occurring only in poetry and late prose (in Job, 41 times). The same divine name is found in Arabic (ilah) and in Aramaic (elah). The singular is used in six places for heathen deities (II Chron. 32:15; Dan. 11:37, 38; etc.); and the plural also, a few times, either for gods or images (Ex. 9:1, 12:12, 20:3; etc.) or for one god (Ex. 32:1; Gen. 31:30, 32; etc.). In the great majority of cases both are used as names of the one God of Israel.
The root-meaning of the word is unknown. One theory is that it may be connected with the old Arabic verb alih (to be perplexed, afraid; to seek refuge because of fear). Eloah, Elohim, would, therefore, be "He who is the object of fear or reverence," or "He with whom one who is afraid takes refuge".
The word El appears in Assyrian (ilu) and Phenician, as well as in Hebrew, as an ordinary name of God. It is found also in the South-Arabian dialects, and in Aramaic, Arabic, and Ethiopic, as also in Hebrew, as an element in proper names.
It is used in both the singular and plural, both for other gods and for the God of Israel. As a name of God, however, it is used chiefly in poetry and prophetic discourse, rarely in prose, and then usually with some epithet attached, as "a jealous God." Other examples of its use with some attribute or epithet are: El 'Elyon ("most high God"), El Shaddai ("God Almighty"), El 'Olam ("everlasting God"), El Hai ("living God"), El Ro'i ("God of seeing"), El Elohe Israel ("God, the God of Israel"), El Gibbor ("Hero God").
The name Shaddai, which occurs along with El, is also used independently as a name of God, chiefly in the Book of Job. According to Ex. vi. 2, 3, this is the name by which God was known to Abraham, Isaac, and Jacob.
The name Elyon occurs with El, with YHVH, with Elohim, and also alone. It appears chiefly in poetic and later Biblical passages.
The names Yhwh and Elohim frequently occur with the word tzevaot ("hosts"), as YHVH Elohe tzevaot ("YHVH God of Hosts") or "God of Hosts"; or, most frequently, "Yhwh of Hosts." To this last Adonai is often prefixed, making the title "Lord Yhwh of Hosts."
This compound divine name occurs chiefly in the prophetic literature and does not appear at all in the Pentateuch or in Joshua or Judges. The original meaning of tzevaot may be found in I Sam. xvii. 45, where it is interpreted as denoting "the God of the armies of Israel". The word, apart from this special use, always means armies or hosts of men, as, for example, in Ex. vi. 26, vii. 4, xii. 41, while the singular is used to designate the heavenly host.
The name Ehyeh denotes God's potency in the immediate future, and is part of YHVH. The phrase "ehyeh-asher-ehyeh" (Ex. iii. 14) is interpreted by some authorities as "I will be because I will be," using the second part as a gloss and referring to God's promise, "Certainly I will be [ehyeh] with thee" (Ex. iii. 12). Other authorities claim that the whole phrase forms one name. The Targum Onkelos leaves the phrase untranslated and is so quoted in the Talmud (B. B. 73a). The "I AM THAT I AM" of the Authorized Version is based on this view.
The name Yah is composed of the first letters of YHVH. See also the Rastafarian Jah.
According to Jewish tradition, the sacredness of the divine names must be recognized by the professional scribe who writes the Scriptures, or the chapters for the tefillin and the mezuzah. Before transcribing any of the divine names he prepares mentally to sanctify them. Once he begins a name he does not stop until it is finished, and he must not be interrupted while writing it, even to greet a king. If an error is made in writing it, it may not be erased, but a line must be drawn round it to show that it is canceled, and the whole page must be put in a genizah and a new page begun.
According to Jewish tradition, the number of divine names that require the scribe's special care is seven: El, Elohim, Adonai, Yhwh, Ehyeh-Asher-Ehyeh, Shaddai, and Tzevaot.
However, R. Jose considered tzevaot a common name (Soferim iv. 1; Yer. R. H. i. 1; Ab. R. N. xxxiv). R. Ishmael held that even Elohim is common (Sanh. 66a). All other names, such as Merciful, Gracious, and Faithful, merely represent attributes that are common also to human beings (Sheb. 35a).
The prohibition of blasphemy, for which capital punishment is prescribed, refers only to the Name proper, YHVH (Soferim iv., end; comp. Sanh. 66a).
In many of the passages in which "elohim" occurs in the Bible it refers to gentile deities, or in some instances to powerful men (comp. Gen. 3:5), to judges (Ex. 21:6), or to Israel (Ps. 81:9, 82:6). Adonai sometimes refers to a distinguished person.
The Talmud says Shalom ("Peace"; Judges vi. 23) is a name of God; consequently one is not permitted to greet another with the word "shalom" in unholy places (Talmud, Shabbat 10b). The name Shelomoh (from shalom) refers to the God of Peace, and the Rabbis assert that the Song of Solomon is a dramatization of the love of God: "Shalom" to His people Israel = "Shulamite."