البحر كبير.

In Arabic, the verb to be is usually not written or spoken in the present tense.

So:

• البحر كبير = The sea is big

Literally, it is more like:

• the-sea big

This is completely normal in Arabic.
If you wanted was, then Arabic would use a verb, such as:

• كان البحر كبيرًا = The sea was big

This is the normal order for a simple equational sentence like this in Arabic:

• البحر = the subject
• كبير = the description/predicate

So Arabic is following a pattern like:

• [noun] + [adjective/description]

That gives:

• البحر كبير = The sea is big

You can sometimes move parts around in Arabic for emphasis, but البحر كبير is the basic, neutral order.

ال is the Arabic definite article, meaning the.

So:

• بحر = sea
• البحر = the sea

In this sentence, the noun is definite because we are talking about the sea, not just a sea.

This is very common in Arabic nominal sentences.

• البحر is definite: the sea
• كبير is indefinite in form, but here it functions as a predicate, not as a separate noun phrase

So كبير means big as a description of البحر.

Compare:

• البحر كبير = The sea is big
• البحر الكبير = the big sea

That second phrase is different. In البحر الكبير, الكبير is an adjective directly modifying البحر, so both words are definite.

This is an important difference.

• البحر كبير = The sea is big
  This is a complete sentence.

• البحر الكبير = the big sea
  This is just a noun phrase, not a full sentence by itself.

Why?

In Arabic, when an adjective directly describes a noun inside a noun phrase, it usually matches it in definiteness:

• البحر = the sea
• الكبير = the big

So:

• البحر الكبير = the big sea

But when the second word is the predicate in a sentence, it does not take ال:

• البحر كبير = The sea is big

Yes. Arabic adjectives and predicate adjectives normally agree with the noun in:

• gender
• number
• definiteness when they are attributive adjectives

Here, البحر is:

• masculine
• singular

So the form كبير is also:

• masculine
• singular

If the noun were feminine, you would usually use كبيرة instead.

For example:

• البحيرة كبيرة = The lake is big

Because بحر is a grammatically masculine noun in Arabic.

Grammatical gender in Arabic does not always match biological sex. Many inanimate objects are either masculine or feminine simply as part of the language.

So:

• بحر = masculine
• therefore the adjective is كبير, not كبيرة

A careful pronunciation is:

• al-baḥru kabīr

In normal pause, many learners will hear or say something closer to:

• al-baḥr kabīr

A few notes:

• ḥ in baḥr is a strong h-like sound from deeper in the throat
• ī in kabīr is a long ee sound
• The r is rolled or tapped

In everyday reading, short vowels are often not written, so learners usually see:

• البحر كبير

instead of the fully vowelled form:

• اَلْبَحْرُ كَبِيرٌ

In fully vowelled Modern Standard Arabic, the sentence is:

• اَلْبَحْرُ كَبِيرٌ

The endings are:

• البحرُ with -u
• كبيرٌ with -un

Why?

• البحرُ is the subject of the nominal sentence, so it takes ḍamma
• كبيرٌ is the predicate, and in a fully inflected form it also takes ḍamma and tanwīn if it is indefinite

However, in normal modern writing and in pause, these case endings are often not pronounced.

The ending changes because of case and grammatical role.

In this sentence:

• البحر كبيرٌ = big is the predicate of a nominal sentence, so it is nominative

But in other structures, it may change. For example:

• كان البحر كبيرًا = The sea was big

Here كبيرًا is the predicate of كان, so it is in the accusative.

So the basic stem is كبير, but the ending changes depending on grammar.

It is a nominal sentence in Arabic.

That means it begins with a noun, not a verb:

• البحر = noun
• كبير = adjective/predicate

Arabic has two major sentence types:

• nominal sentences: often begin with a noun
• verbal sentences: begin with a verb

Since البحر كبير starts with a noun and has no present-tense verb, it is a nominal sentence.

Possibly, depending on context, but the most direct meaning of كبير is big or large.

Arabic adjectives can sometimes be broader in meaning than a single English word. In some contexts, كبير can also suggest:

• great
• important
• major

But in a simple sentence like البحر كبير, the most natural meaning is:

• The sea is big

بحر كبير by itself usually means:

• a big sea

It is a noun phrase, not normally A sea is big.

To say A sea is big as a full sentence, Arabic would usually need a clearer context, because that sentence is not very natural in English or Arabic without more information.

So remember:

• بحر كبير = a big sea
• البحر كبير = The sea is big

This difference is very useful:

• noun + adjective together as one phrase = description inside a noun phrase
• definite noun + indefinite adjective = often a full sentence meaning X is Y