[lojban] Re: and/or

[Penguino <spheniscine@gmail.com>]

There are several series of connectors in Lojban. Each one deals with a different scope. Each series comes with four flavors, each represented by a different final vowel:
-a P OR Q, inclusive
-e P AND Q
-o P IFF Q, if and only if, or truth equivalence. Either both are true, or neither are.
-u P, P regardless of Q

Each one can be modified further by negating either side (na on the left and nai on the right) or both. The -u series may also be inverted to "P or not, but definitely Q", by use of 
se. (Technically, you can also do that to the other series, but it doesn't change their meaning.)

Case I:
Bears killers came into the city.
The sentence means that every object which came into the city is bear AND killer simultaneously.

loi cribe je catra cu nerkla le tcadu

The j- series of logical connectors are used within tanru, and connect the two brivla. Thus "cribe je catra" refers to something that is a bear AND a killer.
 

Case II:
Bears and killers came into the city.
The sentence means that every object which came into the city is EITHER bear OR killer.
Here one  can distinguish two sub-cases.

II A: the object cannot be bear and killer simultaneously. 

II B: the object can be bear and killer simultaneously.

Now this is a little difficult. The normal translation of the English sentence would be:

loi cribe .e loi catra cu nerkla le tcadu

In this case, it is claiming that both the propositions "Bears came into the city" and "Killers came into the city" are true. These require connecting the sumti "loi cribe" and "loi catra". For this, one simply uses the vowel itself. This does not say anything about whether the objects can be bears and killers. This also does not say that they came together. To show that they came together, joi is needed:

loi cribe ku joi loi catra cu nerkla le tcadu

(note the ku; it is there because joi can connect both tanru and sumti.) This binds loi cribe and loi catra into a single group. Again, this does not negate objects that are bears and killers.

For the senses you gave, one could of course, use tanru connectors like so:
1. loi cribe ja catra cu nerkla le tcadu
2. loi cribe jonai catra cu nerkla le tcadu

These sentences are hard to translate into English. In sentence 1, it is describing a mass of things that are bears OR killers, or maybe both. In sentence 2, it is describing a mass of things that are either bears or killers, and not both. (Exclusive-or is produced by negating either side of -o). But neither preclude the group being all bears and no killers or all killers and no bears.

Case III:
Bears or killers came into the city.
The sentence means that one of the following two sentences is correct (but I do not know which one):
1. Bears came into the city.
2. Killers came into the city.
Here one can also distinguish two sub-cases:
III A: I do not know which of the two above sentences is correct but I know that only one of them is correct.

loi cribe .onai loi catra cu nerkla le tcadu

This is connection between sumti, so the single vowel is used. As discussed above, exclusive-or is produced by negating either side of iff.
 

III B: At least one (may be two) sentences are correct. 

loi cribe .a loi catra cu nerkla le tcadu
 

Connection between sumti, inclusive-or.