Kailangan pang plantsahin ang pantalon ko.

Here, pang is basically pa plus the linker -ng.

• pa means still, yet, or in addition
• -ng links it to the next word

So kailangan pang plantsahin means that ironing is still necessary; it has not been done yet.

Also, this is not the separate affix pang- that can mean something like for use in / for in other words.

Plantsahin is the verb form meaning to iron something.

The base word is plantsa (an iron / to iron), and -hin makes it a verb that focuses on the thing being acted on. In this sentence, the thing affected is ang pantalon ko, so plantsahin is the natural form.

A useful comparison:

• Plantsahin ang pantalon ko. = Iron my pants.
• Ang pantalon ko ay plantsahin. is not the normal way to say it.

So plantsahin is the correct verbal form for to iron the pants.

Because ang pantalon ko is the item being highlighted as the thing that needs the action.

In Filipino, the marker ang often marks the noun phrase that is in focus or is the main topic of the clause. Since the sentence is built around the pants as the thing that needs ironing, ang is used.

If you used ng, the structure and meaning would change.

In Filipino, possessive pronouns usually come after the noun.

So:

• pantalon ko = my pants
• bahay ko = my house
• kaibigan ko = my friend

This is normal Filipino word order. English puts the possessive before the noun; Filipino usually puts it after.

Yes. The sentence does not explicitly say who will iron the pants.

That is very normal in Filipino. The sentence only says that the pants still need to be ironed. It leaves the doer unstated.

If you want to say I still need to iron my pants, you would usually say:

• Kailangan ko pang plantsahin ang pantalon ko.

That ko before pang means I am the one who has to do it.

So:

• Kailangan pang plantsahin ang pantalon ko. = the pants still need ironing
• Kailangan ko pang plantsahin ang pantalon ko. = I still need to iron my pants

Kailangan means necessary, needed, or need depending on the sentence.

In this sentence, it works as the main predicate: it is necessary to iron my pants / my pants need to be ironed.

It does not behave exactly like an ordinary English verb such as need. In Filipino, kailangan often acts more like a predicate meaning necessary and then takes a complement:

• Kailangan ko ng tubig. = I need water.
• Kailangang umalis. = It is necessary to leave.
• Kailangan pang plantsahin ang pantalon ko. = My pants still need ironing.

Because Filipino normally likes predicate-first word order.

So it is very natural to start with the predicate:

• Kailangan pang plantsahin = still needs to be ironed
• ang pantalon ko = my pants

That gives the full sentence:

• Kailangan pang plantsahin ang pantalon ko.

English speakers often expect the noun first, but Filipino very often puts the predicate first in neutral statements.

Because the linker goes with the word that comes directly before the word it connects to.

Without pa, you can say:

• Kailangang plantsahin ang pantalon ko.

Here, -ng is attached to kailangan to link it to plantsahin.

But when pa is inserted before plantsahin, the linker moves to that word:

• Kailangan pa-ng plantsahin ang pantalon ko
• written as Kailangan pang plantsahin ang pantalon ko

So the linker is attached to pa, not to kailangan, because pa is now the word directly before plantsahin.

In Filipino, nouns usually do not change form for singular and plural the way English nouns do.

So pantalon can refer to pants/trousers as a garment. Even though English uses a plural-looking word (pants), Filipino just uses pantalon.

The exact number usually depends on context.

This is a very important contrast.

• pa = still / not yet finished
• na = already / now

So:

• Kailangan pang plantsahin ang pantalon ko. = My pants still need ironing.
• Naplantsa na ang pantalon ko. = My pants have already been ironed.

So pa shows that the action is not done yet, while na usually shows that something is already done or has already changed.

It is a very common Filipino word, but it is historically a borrowing. It comes from plantsa, which is borrowed from Spanish.

That is extremely common in Filipino vocabulary, especially for everyday household actions and objects. Even though it is borrowed, plantsahin is completely normal and natural in everyday speech.