المتطوع يجمع النفايات البلاستيكية.

الـ is the Arabic definite article, equivalent to the.

In this sentence it appears in:

• المتطوع = the volunteer
• النفايات = the waste / the trash
• البلاستيكية = the plastic

A useful rule: when a noun is definite, its adjective is also usually definite. That is why both النفايات and البلاستيكية have الـ.

المتطوع is a noun meaning the volunteer. More specifically, it is an active participle from the verb تطوّع (to volunteer).

So it literally means something like the one who volunteers.

It is:

• masculine
• singular
• definite

If you wanted the feminine singular, you would say المتطوعة.

يجمع is the imperfect form of the verb جمع.

In beginner-friendly terms, it can mean:

• collects
• is collecting
• sometimes does collect

So Arabic يجمع does not map to just one English tense. The exact meaning depends on context.

Its grammatical features here are:

• 3rd person
• masculine
• singular

The fully vocalized form is يَجْمَعُ.

Because Arabic verbs already show the subject information.

يجمع already tells you:

• he
• singular
• masculine

So Arabic does not need a separate pronoun here.

You could add هو (he) for emphasis, but it is not necessary:

• هو يجمع النفايات البلاستيكية = He is collecting the plastic waste

Without emphasis, the shorter version is more natural.

Both orders are possible in Arabic.

This sentence uses subject–verb–object order:

• المتطوع يجمع النفايات البلاستيكية

But you can also say:

• يجمع المتطوع النفايات البلاستيكية

That verb-first order is also correct and is often felt to be a bit more formal or more typical of traditional written Arabic.

For a learner, the important point is:

• both are grammatical
• the sentence you were given is a very common and clear pattern

In Arabic, adjectives normally come after the noun they describe.

So:

• النفايات البلاستيكية = the plastic waste

This is the normal order in Arabic:

• noun + adjective

Also, the adjective usually matches the noun in definiteness, which is why البلاستيكية also has الـ.

This is a very common Arabic rule.

النفايات is a non-human plural noun. In Modern Standard Arabic, non-human plurals usually take feminine singular agreement in adjectives.

So although النفايات is plural, the adjective appears as feminine singular:

• النفايات البلاستيكية

This is called deflected agreement.

So the pattern is normal:

• non-human plural noun
• feminine singular adjective

You will see this a lot in MSA.

النفايات is plural.

Its singular is نفاية, meaning a piece of waste / trash / refuse.

So:

• نفاية = one waste item / one piece of trash
• نفايات = waste / trash / wastes

Even though English often treats waste or trash as an uncountable mass noun, Arabic often uses a plural form like نفايات.

You do not pronounce it as al-nifāyāt in careful Arabic pronunciation.

Because ن is a sun letter, the l of الـ assimilates to it. So it is pronounced:

• an-nifāyāt

By contrast:

• المتطوع keeps the l sound, because م is a moon letter
• البلاستيكية also keeps the l sound, because ب is a moon letter

So the sentence is pronounced approximately:

• al-mutaṭawwiʿ yajmaʿ an-nifāyāt al-bilāstīkiyya

In normal Arabic writing, short vowels and most case endings are usually not written.

So you commonly see:

• المتطوع يجمع النفايات البلاستيكية

In a fully vocalized version, you might see:

• المتطوعُ يَجمعُ النفاياتِ البلاستيكيةَ

A few notes:

• المتطوعُ has ـُ because it is the subject
• يَجمعُ has its normal imperfect ending
• النفاياتِ is the direct object, and because it is a sound feminine plural, it takes kasra in the accusative
• البلاستيكيةَ matches the whole noun phrase as an adjective

In everyday reading, learners usually meet the unvocalized version.

In traditional Arabic grammar, this is usually analyzed as a nominal sentence because it begins with a noun:

• المتطوع

The rest, يجمع النفايات البلاستيكية, is a verbal clause functioning as the predicate.

But for a learner, it is completely fine to understand it simply as:

• subject + verb + object

That practical analysis is often the most useful at this stage.

For a female singular volunteer:

• المتطوعة تجمع النفايات البلاستيكية

For plural male or mixed volunteers:

• المتطوعون يجمعون النفايات البلاستيكية

If you use verb-first order with a plural subject, you can also say:

• يجمع المتطوعون النفايات البلاستيكية

And notice:

• النفايات البلاستيكية stays the same
• the adjective البلاستيكية remains feminine singular because النفايات is a non-human plural noun