هذه النظارات الواقية جديدة.

A natural breakdown is:

• هذه = this / these
• النظارات = the glasses / the goggles
• الواقية = protective
• جديدة = new

So the structure is basically:

• هذه النظارات الواقية = these protective glasses
• جديدة = are new

Yes, هذه is basically the feminine singular demonstrative, but Arabic often uses the feminine singular form with non-human plurals.

Since النظارات is a non-human plural noun, هذه can mean these here.

So:

• هذه النظارات = these glasses

This is very normal in Modern Standard Arabic.

هؤلاء is mainly used for plural people or other rational beings.

Examples:

• هؤلاء الطلاب = these students
• هؤلاء المعلمات = these female teachers

But النظارات is a thing, not a person, so Arabic treats it differently. With non-human plurals, MSA usually uses feminine singular agreement, so هذه is the expected choice.

That is a very common question. In Arabic, when a demonstrative like هذا / هذه / هؤلاء comes before a noun, the noun is usually still definite, and it normally keeps الـ.

So Arabic says:

• هذه النظارات
  literally something like
• these the-glasses

But the correct English translation is simply:

• these glasses

This is just a normal difference between Arabic and English structure.

Because adjectives normally come after the noun in Arabic.

So:

• النظارات الواقية = the protective glasses
• literally: the glasses protective

This is the usual Arabic order:

• noun first
• adjective after it

This is one of the most important grammar points in Arabic.

Non-human plural nouns in MSA usually take feminine singular agreement. This is often called deflected agreement.

So even though النظارات is plural in meaning, the adjectives after it appear in the feminine singular:

• الواقية not الواقيات
• جديدة not جديدات

That is why the sentence is:

• هذه النظارات الواقية جديدة

not normally:

• هذه النظارات الواقيات جديدات

Because they do two different jobs.

1. الواقية is an attributive adjective

It is part of the noun phrase النظارات الواقية = the protective glasses.

Since it directly describes a definite noun (النظارات), it must match it in definiteness:

• النظارات = definite
• الواقية = also definite

2. جديدة is the predicate

It tells us something about the subject:

• These protective glasses are new

Predicate adjectives in this kind of Arabic sentence are usually indefinite, so جديدة does not take الـ.

So the contrast is:

• النظارات الواقية = the protective glasses
• جديدة = new

Because Arabic often leaves out the verb to be in the present tense.

So:

• هذه النظارات الواقية جديدة literally looks like
• these protective glasses new

But the meaning is:

• These protective glasses are new

This is a standard Arabic nominal sentence.

If you wanted a past tense meaning, you would usually use كان:

• كانت هذه النظارات الواقية جديدة = These protective glasses were new

The singular is نظارة.

The plural is نظارات.

In real usage, نظارات can refer to a single pair of glasses or goggles, much like English uses glasses as a plural form for one item. So even when talking about one pair, Arabic may still use the plural form.

That makes this word feel fairly natural to English speakers, since English does something similar.

With full case endings, it is:

• هٰذِهِ النَّظَّارَاتُ الوَاقِيَةُ جَدِيدَةٌ

A common transliteration is:

• hādhihi an-naẓẓārātu al-wāqiyatu jadīdatun

Why these endings?

• النظاراتُ is nominative as the subject
• الواقيةُ matches it
• جديدةٌ is also nominative as the predicate

In normal pauses and in most everyday reading, those final case endings are often not pronounced clearly.