شارعنا ليس هادئا في المساء، لكن البيت هادئ بعد أن نغلق النوافذ.

شارعنا is made of:

• شارع = street
• ـنا = our

In Arabic, possessive pronouns attach directly to the noun, so it becomes one word.

Also, a noun with a possessive suffix is already definite, so you do not add الـ.

Compare:

• شارع = a street / street
• الشارع = the street
• شارعنا = our street

So الشارعنا would be incorrect.

Because here هادئ is the predicate of the sentence, not an attributive adjective.

• البيت هادئ = the house is quiet
• البيت الهادئ = the quiet house

That is an important difference in Arabic:

• noun + indefinite adjective/predicate often means X is Y
• noun + matching definite adjective means the Y noun

So in this sentence, هادئ / هادئًا means quiet as the description being asserted, not the quiet as part of a noun phrase.

ليس is the normal way to negate a nominal sentence in the present.

The positive sentence would be:

• شارعنا هادئ في المساء = our street is quiet in the evening

To negate that, Arabic commonly uses:

• شارعنا ليس هادئًا في المساء = our street is not quiet in the evening

So ليس is functioning like is not here.

A learner should think of it this way:

• ليس often negates X is Y
• لا is more commonly used with verbs, general negation, or set expressions

This is about case.

With ليس:

• the subject stays nominative
• the predicate becomes accusative

So:

• شارعنا ليس هادئًا

But in a regular nominal sentence:

• the subject is nominative
• the predicate is also nominative

So:

• البيت هادئٌ

In unvocalized text, those endings are often not written, but grammatically the full forms are:

• هادئًا after ليس
• هادئٌ in البيت هادئٌ

Because normal Arabic writing usually leaves out most short vowels and case endings.

So in everyday text, you often see:

• هادئ
• البيت هادئ

But in a fully vocalized version, it would be:

• هادئًا after ليس
• هادئٌ after البيت

This is very common in Arabic texts. Learners often need to infer the grammar from context.

Here لكن means but or however.

It introduces a contrast:

• شارعنا ليس هادئًا في المساء
• لكن البيت هادئ...

This لكن is the simple conjunction and does not change the case of the next word.

That is different from لكنَّ, which is a grammatical particle like إنَّ and affects the noun after it.

So in this sentence, think of it as plain but.

Arabic often uses the definite article with parts of the day and other time expressions.

So these are very natural:

• في الصباح = in the morning
• في المساء = in the evening
• في الليل = at night

Using المساء here is normal and idiomatic. It does not sound unusually specific; it simply means in the evening.

بعد أن means after followed by a clause.

So:

• بعد أن نغلق النوافذ = after we close the windows

Very literally, it is something like:

• after that we close the windows

In natural English, you can translate it as:

• after we close the windows
• after closing the windows

depending on style.

The prefix نـ marks first person plural in the present tense, so:

• نغلق = we close / we shut

Compare:

• أغلق = I close
• تغلق = you close / she closes
• يغلق = he closes
• نغلق = we close

So the sentence says after we close the windows.

Because أغلق is the past tense / dictionary form, while نغلق is the present tense.

This verb follows the pattern:

• أغلق = he closed / to close
• يُغلق = he closes
• نُغلق = we close

So when the present-tense prefix is added, the form changes. That is why you do not keep the initial أ of أغلق.

Also, after أن, the verb is grammatically in the subjunctive, though in ordinary unvocalized writing it still looks the same:

• أن نُغلقَ

The singular is:

• نافذة = window

The plural is:

• نوافذ = windows

This is a broken plural, which means the inside shape of the word changes rather than just adding a simple ending.

That is very common in Arabic. So this is something learners simply have to get used to:

• نافذة → نوافذ

With الـ, it becomes the windows:

• النوافذ

Here it refers to the specific windows of the house, so the definite form makes sense.