“Mabil
ís” and “kabil
ís” are both about being fast, but they don’t mean the same thing.
“Kabilis” is a comparative adjective. It is actually “kas
íng bil
ís” that becomes “kabil
ís” when, as @jkos correctly said, it follows “gaano (like how much)”, “ganito (like this/this way)”, ganiyan/ganyan (like that/that way)”, and “ganoon/ganun (like that yonder/way or a conceptual that)”. There should be a linker “na” between those four words (modifiers) and “kabilis”, but some speakers omit it.
1. Kas
íng bil
ís ng an
ó? = Gaanong kabilis? = As fast as what?/How fast?
2. Kasing bilis nit
ó = Ganitong kabilis = As fast as this/This fast
3. Kasing bilis niy
án/n’yan = Ganiyang/Ganyang kabilis = As fast as that/That fast
4. Kasing bilis no
on/nun = Ganoong/Ganung kabilis = As fast as that (yonder)/That fast
Kasing bilis ng ano (kung/kapag/pag) tumakbo so Anna? = Gaanong kabilis (kung/kapag/pag) tumakbo si Anna? – “Kung/kapag/pag” is “when”. It may be, and usually is, omitted, especially with the “kabilis” version of the sentence. I also hear “kung” used a lot more often than “kapag” or “pag”. The literal translation is “As fast as what/How fast is it when Anna runs?”, but we would normally translate that as “How fast does Anna run?”.
When you use sentences 2 – 4, the basis of comparison must be already clear or understood.
Kas
íng bilis n’yan/Gany
áng kabil
ís (kung) tumakb
ó si Anna. = Anna runs as fast as that. – The “that” is something/someone whose running speed was just observed or is already known to the persons having the conversation.
Also, “kasing…” may be used with a noun, but that’s not done with “ka-” because “ka-“ has to have a modifier before it. Hence, the latter may only be used after the basis for comparison has already been established.
KAS
ÍNG LAK
ÁS ni Hercules ang tatay ko. GAN
ÚNG KALAK
ÁS ang tatay ko. = My dad is AS STRONG AS Hercules. My dad is THAT STRONG/AS STRONG AS THAT.
Jack: KASING BILIS ng cheetah kung tumakbo si Anna. = Anna runs AS FAST AS a cheetah.
Jill: GANOONG KABILIS? Impos
ibleng GANUNG KABILIS tumakbo si Anna. = THAT FAST? It’s impossible for Anna to run THAT FAST/AS FAST AS THAT. (If you want to use “kasing bilis” in the second sentence, it becomes “Imposibleng kasing bilis ng cheetah kung tumakbo si Anna”.)
Mas nak
ákatuw
â siy
á, pero HIND
Í siy
á GAN
ÚNG KABIL
ÍS. = He/She/It is more fun/enjoyable, but he/she/it is NOT THAT FAST. – The basis for comparison or the “that” must have already been stated beforehand.
Mas nakakatuwa siya, pero HINDI siya MABIL
ÍS. = He/She/It is more fun/enjoyable, but he/she/it is NOT FAST. – No comparison is made.