First, those words do not always refer to G-d, just as the word god does not always refer to G-d. Elokim is a word used to mean judges, and thus you and I may also say the word "Elohim" when we are referring to judges. Similarly, "my master" can either refer to "my Master" (i.e. G-d), or it can refer to anyone with whom you are speaking with deference. Hence, Avraham Avinu was talking to the oldest of his guests when he said, "Adonai," a phrase of deference. You and I can also use that word when refering to someone with deference.

Second, there are Halachic opinions that maintain that even the word "Elo-him" that refers to G-d may be used by us in informal speech (i.e. outside of prayers and blessings), since it is a word that means G-d and just like we say that word in English ("G-d"), we can say it in Hebrew as well. However, the accepted practice is not to use that word in informal speech, out of honor and respect for G-d. The same, in theory, applies to "Ado-nai," but since that word is what we use in place of the Tetragrammaton, which is forbidden to say, we are stringent and do not say it outside of blessings and prayers. It is interesting to note that the authorities rule that we may not use any word in any language that means G-d (such as the word "G-d") in vain (i.e. not for an important, holy purpose).

Y. Shaw