البشر يحتاجون إلى الماء.

A careful full reading with case endings is:

al-basharu yaḥtājūna ilā al-māʾi

In normal pause-style reading, learners often hear something closer to:

al-bashar yaḥtājūn ilā al-māʾ

A few pronunciation notes:

• ح in يحتاجون is a deeper, breathier h sound than English h.
• ā in إلى and الماء is a long aa sound.
• ء at the end of الماء is a hamza, a glottal stop, so māʾ ends with a little catch in the throat.

Because Arabic often uses ال to talk about a whole class or category in a generic sense.

So البشر here means something like:

• human beings
• humankind
• people in general

This is different from English, where we often use no article for general statements, as in Humans need water. In Arabic, using ال in this kind of generic statement is very normal.

It behaves like a collective/generic noun meaning humans / humankind.

That is why it can feel a little unusual to an English speaker:

• its form does not look like a regular plural such as مسلمون
• but its meaning is plural or collective

In this sentence, it is understood as referring to human beings as a group, so a plural verb is used: يحتاجون.

Because the subject refers to human beings as a group.

يحتاجون is the present tense, third-person masculine plural form of the verb احتاج إلى.

So the ending -ون tells you the subject is they.

Also, Arabic normally uses the masculine plural as the default for mixed groups or for people in general. Since البشر means humanity in general, masculine plural agreement is natural here.

The dictionary form you would usually learn is:

احتاج إلى = to need

From that verb:

• هو يحتاج إلى = he needs
• هم يحتاجون إلى = they need

So يحتاجون is simply the they form of يحتاج.

Because in Modern Standard Arabic, احتاج normally takes the preposition إلى.

So the pattern is:

• يحتاج إلى شيء = he/it needs something
• يحتاجون إلى الماء = they need water

This is just how the verb is constructed in standard Arabic.
An English speaker may want to say need water directly, but in Arabic the standard pattern is need to/toward water, using إلى.

Because Arabic often uses the definite article with mass nouns and with generic meaning.

So الماء here means water as a general substance, not the specific water in front of us only.

This is very common in Arabic. English often uses no article in these cases, but Arabic frequently prefers ال.

So:

• English: Humans need water
• Arabic: البشر يحتاجون إلى الماء

In fully vocalized formal Arabic, the sentence is:

البشرُ يحتاجونَ إلى الماءِ

Here is why:

• البشرُ has ḍamma because it is the subject.
• يحتاجونَ is in the indicative present tense, so it keeps -ونَ.
• الماءِ has kasra because it comes after the preposition إلى, and prepositions make the following noun genitive.

In normal unvocalized writing, you usually will not see these short vowels, but they are still understood grammatically.

Yes, that is a very normal alternative.

But there is an important grammar point:

• البشر يحتاجون إلى الماء
  Subject first, then verb → the verb shows full plural agreement.

• يحتاج البشر إلى الماء
  Verb first, then subject → in standard Arabic, the verb is often singular when it comes before a plural subject.

So both are possible, but the agreement pattern changes with the word order.

Because م is a moon letter.

In Arabic, the l of ال is:

• pronounced before moon letters
• assimilated before sun letters

Since م is a moon letter, you say:

al-māʾ

not something like am-māʾ.

Sometimes collective nouns in Arabic can be treated differently depending on style and meaning, but for a beginner, the safest and most natural pattern here is the one you see:

البشر يحتاجون إلى الماء

That clearly treats البشر as a group of people and matches it with a plural human verb.

So if you are learning standard usage, this is the form you should be most comfortable with first.