What noun affix is being used in "pangungusap" (engl: "sentence"

The NG in PANG/MANG will take the place of the initial consonant of the root.PaNG + Saliksik
-> PaN + Saliksik: because saliksik root starts with an S.
-> Pa + Naliksik: N replaces S
-> Pa + Nanaliksik: redu
-> PananalisikWhen a root starts with a vowel, NG will also replace the (inexistent) initial consonant of the root.
PaNG + Usap
-> Pa + NGUsap
-> Pa + Ngungusap: redu
-> PangungusapBut there're exceptions like pang-aawit, when "-" added, the root's (inexistent) initial consonant will not be replaced.There're several PANG-s in Filipino. The pang- in PANGhalo is an instrumental pang-(something used for certain purpose), while the PANG in pangungusap and panggagamot is a general nominal pang- or the noun form of MANG-(verb).

@AlexXU Wow, awesome reply. Maraming salamat!

@simpleauthority Ayos lang : )

@AlexXU A followup if you don't mind:> The NG in PANG/MANG will take the place of the initial consonant of the root.It appears this is a sound change grammar rule and not a general rule (but please correct me!)The only nominal affix rules my grammar book lists for pang are:
1. pang + root: instrumental
2. pang + repeat 1st syllable of root + root: nominal action/practice associated w/ rootThe only sound changes I can see when using pang are:
1. Change pang to pan when root starts with d, l, r, s, t and sometimes n
2. Change pang to pam when root starts with b or p or sometimes mWhen combined with nominal pang affix rule 2 (pang + redu + root), then it makes sense with saliksik:pang + saliksik ->
pangsaliksik ->
(redu) pangsasaliksik ->
(sound changes, because saliksik starts with S (sound change rule 1)) pananaliksikBut with usap, there is no such sound change rule presented (usap doesn't begin with any of d, l, r, s, t, n, or b, p, or m) so the change would simply be following rule 2 for me:pang + usap ->
pangusap ->
(redu) panguusapI don't know which rule to lean on to know that the "ng" should be in there. I am just trying to justify the spelling of pangungusap using grammar rules.Is it an exception, or is my grammar book missing a rule that I should know?For example, I can justify gamot:pang + gamot ->
panggamot ->
(redu) panggagamotNo sound changes there because gamot doesn't start with d, l, r, s, t, n, or b, p, or m.Please help me to justify the rules in use here. Thanks!!These are the grammar articles I'm using:
nominal pang rule 1: learningtagalog.com/ grammar/nouns/noun_a ffixes/pang.html
nominal pang rule 2: learningtagalog.com/ grammar/nouns/noun_a ffixes/pang_rep1.htm l
pang sound changes (bottom two of first box): learningtagalog.com/ grammar/forming_and_ connecting_words/sou nd_changes_whenThanks for your help!

@simpleauthority Sorry I forgot to pointed out that
> The NG in nominal PANG- will take the place of the initial consonant of not all, but some of the roots.Please take the sound change and replacement as two processes independent of each other. I'll give more examples to cover all the situations that I can think of:1. no sound change and initial consonant not replaced :
pang + gamot -> panggagamot
pang + gupit -> panggugupit2. root starting with vowel (i.e no sound change) and (inexistent) initial consonant not replaced because of the "-"
pang + away -> pang-aaway
pang + api -> pang-aapi3. sound change but intial consonant not replaced
pang + loko -> panloloko
pang + dukot -> pandudukot4 (compare with situation 1). no sound change and initial consonant replaced:
For all I know, there is no such situation. Correct me if you think of any.5 (compare with sit. 2). roots starting with vowel (i.e no sound change) and (inexistent) initial consonant replaced because there is no "-"
pang + anak -> panganganak
pang + isda -> pangingisda
pang + aso -> pangangaso
pang + usap -> pangungusap6 (compare with sit. 3). sound change and intial consonant replaced
pang + saliksik -> pananaliksik
pang + buhay -> pamumuhay
pang + salita -> pananalitaThe most difficult and interesting thing here is to remember what will happen to a certain root when combined with the nominal PANG-.

@AlexXUGreat write up! -N in general has a lot of sandhi rules in Tagalog but it was interesting to se paN- laid out this way :D