UK Apologetics Reply:
When you see LORD (in block capitals), the specific Hebrew name YHWH is used and it always refers to Him. But the Hebrews thought that this name was too holy to utter so they found various ways around it. The older English translations sometimes translated this to 'Jehovah,' but that was wholly inadequate since there are no vowels in the Hebrew. 'Yahweh' would probably be more accurate.
When one sees lord (first letter not capitalized) in the Old Testament, the word adonai is used in such a way as to refer to a human master or lord; on the other hand, when one sees Lord (first letter capitalized), the same word adonai is used to refer to the true God. When you find 'God,' the Hebrew words elohim, el, or eloah are used to refer to the one true God. Yet at other times, the Hebrew words elohim, el, or eloah are translated as god or gods, referring to idols, spiritual beings, or maybe the objects of other nations' worship.
To go a little deeper then, "LORD" always reflects the original term YHWH (which is found 6,823 times in the KJV), while "Lord" is the English rendition of the Hebrew adonai (used some 300 times). Because the Jews considered the former title to be very sacred, they did not pronounce it. Eventually, the scribes borrowed vowels from the name "Lord" (adonai), but this was based upon a point system which reflected the way the language was spoken. Vowels were thus inserted into the sacred four-letter name (sometimes called the tetragrammaton - "four letters"). This eventually evolved into the dreadful hybrid word "Jehovah" during the twelfth century A.D.
The Hebrew term YHWH is believed to derive from the root hwy, meaning "to be." The name suggests that God simply is, i.e., He possesses an underived existence; He is the eternal "I AM" (see Exodus 3:14 and also John 8:58). This name became a special designation which emphasized God's relationship to the nation of Israel. It dramatically depicts one of the prime attributes of the Creator - His eternal existence. In addition, it stressed his enduring presence, originally with physical Israel, but now with spiritual Israel (the Church) in their redemptive history.
Robin A. Brace. June 1st, 2012.