المسؤول هنا.

Because Arabic usually omits the verb to be in the present tense.

So المسؤول هنا literally looks like the official here, but it means The official is here or The person in charge is here.

This is a very common Arabic pattern called a nominal sentence.

• المسؤول = the official / the person responsible
• هنا = here

In the past or future, Arabic would use an actual verb:

• كان المسؤول هنا = The official was here
• سيكون المسؤول هنا = The official will be here

It is a nominal sentence.

Its two main parts are:

• المسؤول = the subject/topic (مبتدأ)
• هنا = the predicate/comment (خبر)

So the structure is:

• المبتدأ: المسؤول
• الخبر: هنا

The predicate here is an adverb of place functioning as the khabar.

المسؤول can mean several related things depending on context:

• the official
• the person in charge
• the person responsible

In many real situations, The person in charge is here is a very natural translation.

The word comes from the root س-أ-ل, which is related to asking/questioning. Historically, the form suggests someone who is answerable or responsible.

A good pronunciation is:

al-mas-ʔūl

Points to notice:

• الـ is pronounced al-
• م is a moon letter, so the l in al- is pronounced clearly
• the ء is a hamza, a glottal stop, like a brief catch in the throat
• و here gives a long ū

So the word is not masool smoothly; there is a break: mas-ʔūl

The whole sentence is approximately:

al-masʔūlu hunā

Because المسؤول is a noun with the definite article الـ, meaning the.

• مسؤول = an official / a responsible person
• المسؤول = the official / the person in charge

But هنا is not a noun needing the. It is an adverb of place meaning here, so it does not take الـ.

In fully vowelled formal Arabic, it would normally be:

المسؤولُ هنا

Why?

• المسؤولُ takes ḍamma because it is the mubtadaʾ
• هنا is an indeclinable adverb, so it does not change its ending for case in the same way

In everyday writing, those short vowels are usually omitted, so you normally just see:

المسؤول هنا

Yes, you can, but the emphasis changes.

• المسؤول هنا = neutral/default: The official is here
• هنا المسؤول = more marked, often giving extra focus to here or sounding more context-dependent

For a learner, المسؤول هنا is the safest standard version to use first.

A very natural way is:

هنا مسؤولٌ

or

يوجد مسؤولٌ هنا = There is an official here

Why not usually start with مسؤولٌ? Because an indefinite noun at the beginning of a nominal sentence is often less natural unless the context licenses it. Arabic often prefers putting the location first or using يوجد.

So:

• المسؤول هنا = The official is here
• هنا مسؤولٌ = An official is here

It is basically an adverb of place meaning here.

In Arabic grammar, words like هنا can serve as the predicate of a nominal sentence.

So in:

المسؤول هنا

هنا is not an adjective describing المسؤول. It is telling you where the official is.

You would change المسؤول to match the gender/number you want.

• المسؤولة هنا = The female official / the woman in charge is here
• المسؤولون هنا = The officials are here
• المسؤولات هنا = The female officials are here

The word هنا stays the same. It does not change for gender or number.