The English word "if" encompasses a large range of concepts. Sometimes it implies correlation, and sometimes it implies causality. Sometimes it expresses an event happening in a counterfactual world. All of these should be translated differently into Lojban, because they express different concepts.
So, there is no "standard" word or phrase you can use to translate English "if" consistently. The following words can all be used:
- ganai, gi indicates correlation and says nothing about causality.
- go, gi indicates a slightly different correlation and says nothing about causality.
- va'o, fau indicate correlation and say nothing about causality
- mu'ei is an experimental cmavo which incorporates into Lojban logicians' method of handing conditional statements in terms of possible worlds and mu'ei; it has been discussed on the wiki as a means to indicate counterfactual correlation.
- CAhA as sumtcita as a sumtcita may indicate necessity like romu'ei
- bi'ai is the true romu'ei. ca'a is out of this philosophy.
- bai/bapli indicates causality, in the sense that one event compels another to happen.
- ja'e indicates logical causality.
- ki'u/krinu indicates causality by reason/justification/explanation.
- ni'i/nibli indicates causality by logical implication.
- mu'i/mukti indicates causality by motivation/incentive.
- ri'a/rinka indicates causality by physical cause.
- lo du'u xukau is for when you meant to say “whether” (“I don't know if ...”).
ma tadji lenu mi cusku zoi gy. "I would have killed the cat" .gy bau la lojban.
- mi no'omu'eiku pu catra le mlatu
- mi jibni jeku'i se fanta co catra le mlatu
- That only works if you mean that you did in fact to intend to kill the cat. What about "I would have killed the cat, which was running across the road, if I hadn't slammed on the brakes"?
- Couldn't you give other examples than those of killing cats!!!!
- ma tadji lenu mi cusku zoi gy. "I would have killed the platypus" .gy bau la .lojban.
- The Book shows how and it seems rather sufficient.
- .i da'i ganai co'e gi mi ba'o catra le mlatu
- Since the da'i is on the .i, it covers the whole statement.