النت اللاسلكي ثابت.

Because in Arabic, simple present-tense sentences often do not use a separate word for is/am/are.

So:

النت اللاسلكي ثابت
literally looks like: the wireless internet stable

But it naturally means:

The wireless internet is stable.

This is very normal in both Standard Arabic and Egyptian Arabic.
If you want another tense, then a verb usually appears, for example:

• النت اللاسلكي كان ثابت = The wireless internet was stable
• النت اللاسلكي هيبقى ثابت = The wireless internet will be stable

النت is a very common borrowed word in Egyptian Arabic, from English net, meaning internet.

So yes, it is used like a normal Arabic noun in everyday speech. It can even take the Arabic definite article ال-, which is why you get النت = the internet.

You may also see or hear الإنترنت, which is closer to the full formal word internet. In casual Egyptian, النت is extremely common.

Because in Arabic, adjectives usually come after the noun they describe.

So:

• النت اللاسلكي = the wireless internet
• literally: the internet wireless

This is the normal Arabic word order for noun + adjective.

English says wireless internet, but Arabic says internet wireless.

Because when an adjective describes a definite noun in Arabic, the adjective also has to be definite.

So:

• النت = the internet
• اللاسلكي = the wireless

Together, that gives:

النت اللاسلكي = the wireless internet

This is called agreement in definiteness. In Arabic, an attributive adjective usually matches the noun in:

• definiteness
• gender
• number

Compare:

• نت لاسلكي = wireless internet / a wireless internet connection (indefinite)
• النت اللاسلكي = the wireless internet (definite)

Because ثابت is not part of the noun phrase النت اللاسلكي. It is the predicate of the sentence.

The structure is:

• النت اللاسلكي = the subject
• ثابت = the predicate adjective, meaning stable

In Arabic, the predicate in a sentence like this is usually indefinite, so you normally say:

النت اللاسلكي ثابت

not:

النت اللاسلكي الثابت

The version with الثابت would usually sound like the stable wireless internet, where الثابت is just another adjective inside the noun phrase, not the main statement.

A rough Egyptian pronunciation would be:

en-net el-laaselki saabet

A few useful pronunciation notes:

• النت sounds like en-net
  because the l of ال- blends into the n
• اللاسلكي has a doubled l sound, roughly el-laaselki
• ثابت is usually pronounced saabet in Egyptian, because ث is often pronounced like s

So the whole sentence is roughly:

en-net el-laaselki saabet

It is understandable, but in very casual Egyptian, many speakers would often say something more like واي فاي if they specifically mean Wi‑Fi.

For example, in everyday speech you might hear:

• الواي فاي ثابت = The Wi‑Fi is stable
• النت ثابت = The internet is stable

So النت اللاسلكي ثابت is understandable and grammatical, but depending on context, it may sound a bit more formal or less everyday than a sentence with واي فاي.

Because النت is normally treated as a masculine singular noun in Egyptian Arabic, so the predicate adjective matches it.

That is why you get:

• النت ... ثابت

If the noun were feminine singular, you would usually use:

• ثابتة

For example:

• الشبكة ثابتة = The network is stable

So the form ثابت here is showing normal agreement with النت.

Not only that. ثابت has a broader meaning like:

• stable
• steady
• fixed
• constant

With internet or connection-related things, the natural meaning is usually stable or not dropping/cutting out.

So in this sentence, ثابت suggests that the wireless internet is steady and reliable, not fluctuating or disconnecting.

In Egyptian Arabic, the easiest way is to use مش before the predicate:

النت اللاسلكي مش ثابت

That means:

The wireless internet isn’t stable.

This is a very common Egyptian pattern:

• هو تعبان = He is tired
• هو مش تعبان = He is not tired

So for your sentence:

• النت اللاسلكي ثابت = The wireless internet is stable
• النت اللاسلكي مش ثابت = The wireless internet is not stable