See the section for lú on the page about verbs.
Alternate word order: An myau lun. Not allowed: *Lúku an myau; the verb lú agrees with the thing experienced, not the experiencer.
Sye marks that an myau is indefinite. The alternate word order An myau lúsye is still allowed. Note that lúsye doesn't mark agreement with the subject.
Lú by itself often implies sight, but if you want to be clear that you saw the cat (with your eyes), rather than hearing or feeling zem, then you can say this.
Can be used for contrastive focus. Also allowed: Hu kú lun an myau. Not allowed: *Kú lun an myau; because the speaker is experiencing rather than doing, kú must be marked with hu (preposition indicating an experiencer).
Or Lul al myau mausen if you've been talking mainly about him, rather than the cat. The implied experiencer changes when you're talking about what someone else said.
Lam sakipes means intentional looking, as opposed to lú which could just be passive seeing.
Basic example sentence that I'll use to construct more complex examples.
Some alternate word orders allowed: Lú an myau swin swatel, An myau lú swin swatel. Not allowed: *An myau lú(n) swatel: when used in this sense, lú modifies a complete sentence, so the regular verb must be there. Definitely not allowed: *An myau lan saki (swa) swatel: lam saki does translate to "look", but it doesn't mean "look" in this sense, but rather that the cat is looking at something.
This expresses some uncertainty as to whether the cat really is black, or if it just looks that way for some reason. Because of this, the verb changes to the subjunctive (swin instead of swan).
This statement expresses roughly the same amount of certainty as An myau swa-n swatel ("the cat looks black"), but also says that the speaker got the information from direct perception (especially sight). The verb also changes back to the indicative mood.
An myau swa-n swatel lú (with neither the subjunctive nor hwel) is ambiguous between this meaning and the previous meaning, but is allowed in informal speech.
While in English, hear can imply that you were told the information by someone else, in Lwaitel using lú ustelw here would imply that you directly perceived the cat using hearing.
With a verb of emotion, the main sentence is a normal indicative sentence and lú niuspe expresses how the person feels about it. This implies that the fact that the cat is black is known, and the focus is only on the speaker's happiness about it.
Defocusing lú implies that the cat being black is new, important information, and the fact that I'm happy about it is not the main point of the sentence.
...not sure how much sense this makes... need a better noun here. TODO
Lakwe is a noun that must always have a possesser; this is true even if it's indefinite. You could also say Kíku lakwe nga lú yatleng ("I want to befriend someone").
Not *An myau swin swatel lú pwili: that would only be used to contrast with what someone else thinks, or what one thinks at a later time. Also not *An myau swan swatel maus pemim; that means something else (see next example).
This means that the person said, in their head, the sentence "the cat is black", or some paraphrase of it.
Not *An kip lun kiusteng, that's for knowing facts. (I think Spanish is similar in making this distinction.)
Use of "understand" instead of some variant of "to speak" (Swa il hem mausku Lwaitel(?)) is more common.