السفينة كبيرة.

It is a nominal sentence in Arabic, called جملة اسمية.

It has two main parts:

• السفينة = the subject, called مبتدأ
• كبيرة = the predicate, called خبر

So the structure is essentially:

• the ship
  • big

which Arabic uses to mean The ship is big.

In Arabic, the present-tense verb to be is usually not stated.

So:

• السفينة كبيرة literally looks like the ship big
• but it means The ship is big

This is completely normal in Arabic.

If you wanted past tense, Arabic would usually use a form of كان:

• كانت السفينة كبيرة = The ship was big

In this sentence, كبيرة is the predicate, and predicates commonly come after the subject in this kind of sentence.

So the order is:

• السفينة = subject
• كبيرة = what is being said about the subject

That is why Arabic puts them in this order.

Also, Arabic adjectives usually come after the noun they describe, so this word order feels natural to English learners for more than one reason.

Because here كبيرة is not an attributive adjective inside a noun phrase like the big ship. It is the predicate of the sentence: big.

Compare:

• السفينة كبيرة = The ship is big
• السفينة الكبيرة = the big ship

This is a very important difference.

When an adjective directly describes a noun inside one phrase, it usually matches the noun in definiteness:

• سفينة كبيرة = a big ship
• السفينة الكبيرة = the big ship

But in السفينة كبيرة, the second word is not part of the same noun phrase. It is the predicate, so it does not take الـ.

السفينة الكبيرة means the big ship, not The ship is big.

That phrase is just a noun phrase:

• السفينة = the ship
• الكبيرة = the big

Together: the big ship

So:

• السفينة كبيرة = a full sentence
• السفينة الكبيرة = just a phrase

Because السفينة is a feminine noun, and the predicate adjective agrees with it in gender.

• سفينة is grammatically feminine
• so big must be in the feminine form: كبيرة
• not the masculine form كبير

Compare:

• السفينة كبيرة = The ship is big
• البيت كبير = The house is big

So the ending ـة here shows the feminine form.

Yes, that is a big clue.

The ending ـة (called taa marbuta) often marks a noun as feminine. So سفينة is treated as feminine, and anything agreeing with it usually becomes feminine too.

That is why the sentence uses:

• السفينة
• كبيرة

Both are feminine singular.

In fully vocalized Modern Standard Arabic, it would usually be:

السفينةُ كبيرةٌ

Here is why:

• السفينةُ has ـُ because it is the subject of the nominal sentence
• كبيرةٌ has ـٌ because it is an indefinite predicate and nominative

In normal everyday writing, these short vowel endings are usually omitted, so you normally just see:

السفينة كبيرة

Because س is a sun letter.

When الـ comes before a sun letter, the l sound assimilates to the next consonant. So:

• written: السفينة
• pronounced: as-safīnah or as-safīnatu in full reading

The spelling stays the same, but the pronunciation changes.

The final ـة is usually pronounced like -a or -ah when you stop at the word.

So in pause:

• السفينة ≈ as-safīnah
• كبيرة ≈ kabīrah

But when full grammatical endings are pronounced, or when the word is connected in certain structures, the ـة is pronounced as t:

• السفينةُ = as-safīnatu
• كبيرةٌ = kabīratun

So the same letter can sound like:

• -a / -ah in pause
• -t when fully inflected

Yes. سفينة كبيرة means a big ship.

That is different from السفينة كبيرة:

• سفينة كبيرة = a big ship
• السفينة كبيرة = The ship is big

So adding or removing الـ changes the meaning a lot.

In سفينة كبيرة, both words are indefinite and form one noun phrase. In السفينة كبيرة, the first word is definite and the second word is the predicate of a full sentence.