ساحل کنار دریا امن است، اما شب ها همه آنجا نمیمانند.

Persian normally does not use definite articles like English the.

So ساحل can mean:

• the beach
• a beach
• sometimes just beach/coast in a general sense

The exact meaning comes from context. If Persian wants to make a/an clearer, it can use یک:

• یک ساحل = a beach / one beach

In this sentence, ساحل is naturally understood as the beach or the shore from context.

Yes. This is a very common learner question.

You would normally read it as:

• ساحلِ کنارِ دریا
• sâhel-e kenâr-e daryâ

That -e sound is called ezafe. Persian usually does not write short vowels, so the ezafe is often invisible in normal spelling.

Here it links:

• ساحل to کنار دریا
• کنار to دریا

So even though you do not see the -e written, you usually pronounce it.

کنار دریا literally means by the sea or next to the sea.

So:

• ساحل = shore / beach / coast
• کنار دریا = by the sea

Together, the phrase means something like:

• the beach by the sea
• the seashore area
• the shore next to the sea

To an English speaker, this can feel a little repetitive, because beach already suggests the sea. Persian does sometimes use overlapping expressions like this for description or emphasis. You might also hear:

• ساحل دریا
• کنار دریا

Both are common.

امن is an adjective meaning safe or secure.

است means is.

So:

• امن است = is safe

This is a basic Persian pattern:

• noun + adjective + است

For example:

• خانه بزرگ است = The house is big
• اینجا آرام است = It is calm here

In spoken Persian, است is often shortened or softened, but in standard writing امن است is perfectly normal.

شب‌ها literally means nights, but in Persian plural time words are often used to mean a repeated or habitual time.

So شب‌ها can mean:

• at night
• at nights
• during the nights
• night after night, depending on context

In this sentence, it means something like:

• at night
• at night time
• during the nights

This is similar to:

• روزها = during the days / by day
• جمعه‌ها = on Fridays

Also, the standard spelling is usually شب‌ها with a half-space, though learners often also see شب ها.

همه means all or everyone, depending on what it refers to.

Here it refers to people, so the natural meaning is:

• everyone
• all of them

So the second half means roughly:

• but at night, not everyone stays there
• but at night, they do not all stay there

That is an important point: in Persian, a sentence like همه آنجا نمی‌مانند usually means not everyone stays there, not no one stays there.

If you wanted to say no one stays there, Persian would normally say:

• هیچ‌کس آنجا نمی‌ماند

Because همه usually takes a plural verb when it refers to people.

So Persian commonly says:

• همه آمدند = Everyone came
• همه می‌دانند = Everyone knows
• همه آنجا نمی‌مانند = Not everyone stays there

Even though English uses everyone is or everyone does, Persian often uses plural agreement with همه when the meaning is a group of people.

It comes from the verb ماندن = to stay / to remain.

Breakdown:

• مان = present stem
• می‌ = imperfective marker, often used for present habitual or ongoing meaning
• نـ = negative
• -ند = third person plural ending

So:

• می‌مانند = they stay / they are staying
• نمی‌مانند = they do not stay

In this sentence, because of شب‌ها, the meaning is habitual:

• they do not stay there at night
• they don’t remain there at night

Also, standard Persian spelling uses a half-space:

• نمی‌مانند not ideally نمیمانند

Because Persian is usually an SOV language: subject – object/complements – verb.

So Persian often puts place words like آنجا before the verb:

• همه آنجا نمی‌مانند
• literally: everyone there does not stay

This is very normal Persian word order.

English would usually say:

• everyone does not stay there or more naturally:
• not everyone stays there

Persian word order can be somewhat flexible for emphasis, but the verb usually stays near the end.

Yes.

Both اما and ولی mean but.

The difference is mostly style:

• اما = a bit more formal or written
• ولی = very common in everyday speech

So both of these work:

• ساحل کنار دریا امن است، اما شب‌ها همه آنجا نمی‌مانند.
• ساحل کنار دریا امن است، ولی شب‌ها همه آنجا نمی‌مانند.

In a textbook-style sentence, اما sounds perfectly natural.

A useful way to see it is in two parts:

• ساحل کنار دریا امن است
• اما شب‌ها همه آنجا نمی‌مانند

Word-for-word, roughly:

• ساحل کنار دریا = the beach by the sea
• امن است = is safe
• اما = but
• شب‌ها = at night / during the nights
• همه = everyone / all of them
• آنجا = there
• نمی‌مانند = do not stay

So the full pattern is:

• statement 1: X is safe
• contrast: but
• statement 2: at night, not everyone stays there

This is a very common Persian sentence shape: statement + اما/ولی + contrasting statement.