The Old Testament
The Old Testament was mostly written in Hebrew. This language was written using only the consonants; vowels were added later in the form of small signs called “points” which are written in the spaces around and within the letters.
The main words used to refer to God in the Old Testament are the main name of God, which is written with the consonants JHWH (this appears 5521 times in the text) and the titles Elohim (which appears 2250 times) and Adonai (which appears 444 times).
Elohim
The word 'Elohim' is the ordinary word which refers to God. It is sometimes translated as 'Almighty', and could be considered to imply power. It is the first word used to refer to God in the book of Genesis:
"In the beginning, God created the heavens and the earth." (Genesis 1:1)
Adonai
The word 'Adonai' is a word which means 'Lord'; however, it is only used to refer to God or to some being (such as an angel) who is acting as God’s representative, such as in Genesis 18:3 where Abraham addresses an angel who has come to bring a message from God.
It is useful to notice that there is a similar word, 'adon', which also means 'lord', but which is never used of God, but only of human beings; it is used to describe a human being who is important. For example, we find the word used to refer to Abraham in various places. Here is an example:
"The Hittites answered Abraham, 'Hear us, my lord; you are a prince of God among us. Bury your dead in the choicest of our tombs. None of us will withhold from you his tomb to hinder you from burying your dead.'” (Genesis 23:5,6)
There are many other examples.
One passage of great interest is this:
"The LORD says to my Lord: 'Sit at my right hand, until I make your enemies your footstool.'” (Psalm 110:1)
Here the first occurrence of the word 'LORD' (which is entirely in capital letters) is the name JHWH, while the second occurrence (“Lord”) is the word 'adon' - a word reserved for human beings. It is worth noting that the New Testament quotes this passage in no fewer than four places: (Matthew 22:44; Mark 12:36; Luke 20:42 and Acts 2:34) and hence applies this word (which is never used of God) to Jesus.
JHWH
The name by which God is known is written in Hebrew in four letters, JHWH. The problem here is that the name was considered too sacred to be spoken at the time when the vowel points were added to the text, so we cannot be certain exactly how the name was pronounced.
In later centuries readers would say the word 'Adonai' when they encountered JHWH in the text. To remind them to do this the vowels of Adonai were written among the consonants to give the rendering Jehovah; this, however, is almost certainly an incorrect way of pronouncing the name.
As a consequence of the tendency to substitute 'Lord' (Adonai) for the four letter name of God, JHWH, by Hebrew scholars, most modern translations of the Bible use the word 'LORD' (which is often written in capital letters) to indicate the name of God. However, this can be misleading; the word 'LORD' is also used for other names or titles of God.
The meaning of this name of God is explained for us in Exodus chapter 3. This is the account of an encounter between Moses, soon to become the leader of Israel, and God, who revealed himself to Moses through an angel. God commands Moses to lead the Israelites from Egypt, where they are a race of slaves, to the land that God had promised to their forefather Abraham. Moses asks that God should reveal his name, so that he can identify him to the Israelites.
"Then Moses said to God, 'If I come to the people of Israel and say to them, ‘The God of your fathers has sent me to you,’ and they ask me, ‘What is his name?’ what shall I say to them?' God said to Moses, 'I AM WHO I AM.' And he said, 'Say this to the people of Israel, ‘I AM has sent me to you.’" (Exodus 3:13,14)
The name that God reveals to Moses is the name 'I am who I am'; he then shortens it to 'I am'. A simple set of transformations leads to the four letters in the name JHWH; this is God’s name and is used in the next verse:
"God also said to Moses, 'Say this to the people of Israel, ‘The LORD, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you.’ This is my name forever, and thus I am to be remembered throughout all generations.'" (Exodus 3:15)
The name of God is related to the idea of being; but more important, the name reminds us that God is eternal and can therefore guarantee his promises into the far future. This also is emphasised in Exodus 3:15.