@Tisztul_A_Visztula Getting back to the rest of your questions:
About
ľahnúť (si) and
sadnúť (si) - the
si particle may have originally had a distinct "for one's own benefit/pleasure/comfort" meaning at some point in the past - I don't know for sure, I haven't checked - but if it did, this has eroded to the point that dictionaries list the forms with and without
si as synonyms. So, in this sense, there is the verb wihout
si and the verb with the
si firmly attached (reflexivum tantum), and they mean the same. That said, it is interesting to note a few things:
- Talking about people or animals, the verbs
with si are
much more common. (Except
Ľahni! and
Sadni! used as commands for dogs.)
- Talking about inanimate things sagging, descending etc., it's always
without si: Obilie ľahlo. Na mesto sadla tma.
- As I was writing my earlier post about
sadnúť si and
posadiť sa, I was going to say that
sadnúť si v posteli (to sit up in bed) sounds somewhat less good to me than
posadiť sa v posteli, because it's a move to a less comfortable position... But then I checked dictionaries and googled actual usage and realized that this difference is so slight, it's actually illusory...
In contrast, with the verbs
ležať and
sedieť, the basic (
si-less) forms are neutral and
ležať si and
sedieť si have this predictable ethical-dative meaning "just lying/sitting there" (and so they will not be listed in dictionaries as verbs on their own right).
Whether your dictionary is overzealous and lists too many verbs with
sa and
si as separate entries, I can't tell (not knowing your dictionary), but perhaps the authors felt that the forms are frequent enough to merit their own entry, or that they have a special meaning, not just composed of the meaning of the verb and the meaning of
sa or
si.
As
@francisgranada pointed out, usually there is a component of meaning relating to
sa or
si that one can tease out. The difficulty is knowing when the particle is obligatory, when it is optional, how strong a meaning it carries, and which of the several possible meanings it is (as we have seen, the
sa in
Aký pán sa je? turned out not to be reflexive).
For example, the
si seems quite justifiable in
všimnúť si, uvedomiť si, zapamätať si (after all, you are making a mental note
to yourself), but why is it obligatory? And why is it not there in
zbadať or
spozorovať? So, expect to find patterns but not total predictability.