Mahaba ang panahon.

Because Filipino very often puts the predicate first.

In Mahaba ang panahon:

• mahaba = the predicate adjective, long
• ang panahon = the subject/topic, the time/period

So the structure is closer to:

• Long is the period
  rather than the usual English order:
• The period is long

This predicate-first pattern is extremely common in Filipino.

Ang marks the subject/topic of the sentence.

So in Mahaba ang panahon:

• mahaba tells you something about it
• ang panahon tells you what that description is about

A useful way to think of it is:

• ang panahon = the period / the time as the main noun phrase being talked about

It does not mean the exactly in all situations, but in many simple translations it often feels similar.

In simple Filipino sentences like this, a copula such as English is/am/are is often left out.

So:

• Mahaba ang panahon literally looks like Long the period
• but it naturally means The period is long

This is normal Filipino grammar, not an omission or shortcut.

Because mahabang panahon and mahaba ang panahon are doing different jobs.

• mahabang panahon = a long period / long time

  • here, mahaba directly modifies panahon
  • the linker -ng connects them

• mahaba ang panahon = The period is long

  • here, mahaba is the predicate
  • ang panahon is the subject
  • they are not forming one single noun phrase

So:

• mahabang panahon = noun phrase
• mahaba ang panahon = full sentence

Panahon can mean several related things depending on context, such as:

• time
• period
• season
• weather

In a sentence like Mahaba ang panahon, it usually makes most sense as:

• time
• period
• span of time

Context is what decides the best meaning. Filipino words often have a wider range than a single English word.

That is a very common question.

Both can relate to long, but they are used differently:

• mahaba = long in length/extent
• matagal = long in duration / taking a long time

So:

• mahabang panahon = a long period / a long stretch of time
• matagal = for a long time, slow/lasting long

Examples:

• Matagal akong naghintay. = I waited a long time.
• Mahabang panahon iyon. = That was a long period of time.

So mahaba with panahon is possible because you are thinking of time as a stretch or span.

Yes, that is grammatical.

Compare:

• Mahaba ang panahon.
• Ang panahon ay mahaba.

Both mean roughly the same thing.

The difference is mainly in style and focus:

• Mahaba ang panahon = more common, natural predicate-first order
• Ang panahon ay mahaba = more formal, more deliberate, sometimes more emphatic

In everyday speech, the first version is usually more typical.

The simplest way is:

• Hindi mahaba ang panahon. = The period is not long.

You can also soften it:

• Hindi gaanong mahaba ang panahon. = The period is not very long.

Negation usually goes before the predicate.

A simple learner-friendly guide is:

• mahaba → ma-HA-ba
• ang → roughly ahng
• panahon → pa-na-HON

So the whole sentence is approximately:

ma-HA-ba ahng pa-na-HON

Notes:

• ng in ang is the ng sound in sing
• h is pronounced clearly
• stress matters, especially in mahaba and panahon

No, not in the way adjectives change for gender or number in many European languages.

Mahaba stays mahaba whether the noun is singular, plural, masculine, feminine, or inanimate.

For example, the adjective itself does not change like this:

• not something like mahabo / mahabi / mahabas

Instead, Filipino grammar shows relationships through markers like ang, ng, sa, word order, and sometimes linkers such as -ng.

So in this sentence, mahaba stays the same.