You may call someone’s attention to the fact that you are addressing them by using “doi” followed by their name. The sentence
14.1) doi djan.means “Oh, John, I’m talking to you”. It also has the effect of setting the value of “do”; “do” now refers to “John” until it is changed in some way in the conversation. Note that Example 14.1 is not a bridi, but it is a legitimate Lojban sentence nevertheless; it is known as a “vocative phrase”.
Other cmavo can be used instead of “doi” in a vocative phrase, with a different significance. For example, the cmavo “coi” means “hello” and “co'o” means “good-bye”. Either word may stand alone, they may follow one another, or either may be followed by a pause and a name. (Vocative phrases with “doi” do not need a pause before the name.)
14.2) coi. djan.
Hello, John.
14.3) co'o. djan.
Good-bye, John.
Commands are expressed in Lojban by a simple variation of the main bridi structure. If you say
14.4) do tavla You are-talking.you are simply making a statement of fact. In order to issue a command in Lojban, substitute the word “ko” for “do”. The bridi
14.5) ko tavlainstructs the listener to do whatever is necessary to make Example 14.4 true; it means “Talk!” Other examples:
14.6) ko sutra Be fast!
The “ko” need not be in the x1 place, but rather can occur anywhere a sumti is allowed, leading to possible Lojban commands that are very unlike English commands:
14.7) mi tavla ko Be talked to by me Let me talk to you.
The cmavo “ko” can fill any appropriate sumti place, and can be used as often as is appropriate for the selbri:
14.8) ko kurji koand
14.9) ko ko kurjiboth mean “You take care of you” and “Be taken care of by you”, or to put it colloquially, “Take care of yourself”.