It is common to form lujvo that omit the rafsi based on cmavo of selma'o SE, as well as other cmavo rafsi. Doing so makes lujvo construction for common or useful constructions shorter. Since it puts more strain on the listener who has not heard the lujvo before, the shortness of the word should not necessarily outweigh ease in understanding, especially if the lujvo refers to a rare or unusual concept.
Consider as an example the lujvo “ti'ifla”, from the veljvo “stidi flalu”, and meaning “bill, proposed law”. The gismu place structures are:
9.1) “stidi”: agent st1 suggests idea/action st2 to audience st3
“flalu”: f1 is a law specifying f2 for community f3 under conditions f4
by lawgiver f5
This lujvo does not fit any of our existing molds: it is the second seltau place, st2, that is equivalent to one of the tertau places, namely f1. However, if we understand “ti'ifla” as an abbreviation for the lujvo “selti'ifla”, then we get the first places of seltau and tertau lined up. The place structure of “selti'i” is:
9.2) “selti'i”: idea/action se1 is suggested by agent se2 to audience se3Here we can see that se1 (what is suggested) is equivalent to f1 (the law), and we get a normal symmetrical lujvo. The final place structure is:
9.3) f1=se1 is a bill specifying f2 for community f3 under conditions f4
by suggester se2 to audience/lawgivers f5=se3
or, relabeling the places,
9.4) f1=st2 is a bill specifying f2 for community f3 under conditions f4
by suggester st1 to audience/lawgivers f5=st3
where the last place (st3) is probably some sort of legislature.
Abbreviated lujvo like “ti'ifla” are more intuitive (for the lujvo-maker) than their more explicit counterparts like “selti'ifla” (as well as shorter). They don’t require the coiner to sit down and work out the precise relation between the seltau and the tertau: he or she can just rattle off a rafsi pair. But should the lujvo get to the stage where a place structure needs to be worked out, then the precise relation does need to be specified. And in that case, such abbreviated lujvo form a trap in lujvo place ordering, since they obscure the most straightforward relation between the seltau and tertau. To give our lujvo-making guidelines as wide an application as possible, and to encourage analyzing the seltau-tertau relation in lujvo, lujvo like “ti'ifla” are given the place structure they would have with the appropriate SE added to the seltau.
Note that, with these lujvo, an interpretation requiring SE insertion is safe only if the alternatives are either implausible or unlikely to be needed as a lujvo. This may not always be the case, and Lojbanists should be aware of the risk of ambiguity.