الغابة كبيرة.

A common pronunciation is al-ghābah kabīrah.

With full case endings in careful MSA, it is al-ghābatu kabīratun.

A few pronunciation notes:

• غ is a deep, throaty sound, often compared loosely to the French r or the sound in Parisian r.
• ا in غابة gives a long ā sound.
• كبيرة has a long ī sound: ka-bī-ra(h).
• The final ة is usually pronounced -ah or just a light -a when pausing.

In Arabic, the present tense of to be is usually not expressed with a separate word.

So:

• الغابة كبيرة literally looks like the forest big
• but it means the forest is big

This is called a nominal sentence in Arabic. In the present tense, Arabic often just puts:

• the thing being talked about first
• then the description

If you wanted past or future, Arabic would use other words, such as:

• كانت الغابة كبيرة = The forest was big
• ستكون الغابة كبيرة = The forest will be big

Because in this sentence, كبيرة is the predicate: it tells you something about الغابة.

Arabic usually structures this kind of sentence as:

• subject/topic
  • description

So:

• الغابة = the forest
• كبيرة = big

Together: The forest is big.

This is different from English word order, but it is completely normal in Arabic.

This is very important.

• الغابة كبيرة = The forest is big
• الغابة الكبيرة = the big forest

In your sentence, كبيرة is not an adjective attached directly to the noun as part of one noun phrase. It is the predicate of the sentence.

So:

• الغابة كبيرة = a full sentence
• الغابة الكبيرة = a noun phrase

A useful shortcut:

• If both words are definite and side by side, it often means the + adjective + noun phrase
• If the first is definite and the second is indefinite, it can be X is Y

Because الغابة is a feminine noun, so the describing word must agree with it.

Arabic adjectives agree with the noun in:

• gender
• number
• definiteness

Here:

• الغابة is feminine singular
• so the adjective/predicate must also be feminine singular: كبيرة

The masculine form would be كبير.

So compare:

• الغابة كبيرة = The forest is big
• البيت كبير = The house is big

One strong clue is the ending ة, called tāʾ marbūṭah.

Many Arabic nouns ending in ة are feminine, and غابة is one of them.

So:

• غابة = forest, feminine
• كبيرة also ends in ة because it is agreeing with a feminine noun

That said, not every feminine noun ends in ة, and not every noun ending pattern works the same way, but ة is one of the most common signs of a feminine noun.

The letter ة is called tāʾ marbūṭah.

Usually:

• when you stop at the word, it sounds like -ah or -a
• when the word is followed by grammatical endings or is in certain constructions, the t can appear

So in normal pause:

• غابة → ghābah
• كبيرة → kabīrah

But in fully vocalized grammar-focused reading, you may hear:

• al-ghābatu
• kabīratun

And in some constructions, the t is clearly heard, for example:

• غابةُ المدينة = the city’s forest / the forest of the city

In fully vocalized MSA, the sentence is:

الغابةُ كبيرةٌ

This is read as al-ghābatu kabīratun.

Why?

• الغابةُ is the subject of the nominal sentence, so it is in the nominative
• كبيرةٌ is the predicate, and it is also in the nominative

In everyday reading and speech, these short case endings are often not written and are often not pronounced, especially in pause. That is why learners usually first see the sentence as:

الغابة كبيرة

Here, ال is pronounced clearly: al-.

That is because غ is a moon letter, not a sun letter.

So:

• الغابة = al-ghābah

The l sound stays.

Compare that with a sun-letter word, where the l assimilates:

• الشمس is pronounced ash-shams, not al-shams

Since غ is not a sun letter, there is no assimilation here.

They mean different things:

• الغابة كبيرة = The forest is big
• الغابة الكبيرة = the big forest

Why?

• In الغابة كبيرة, the second word is the predicate of a sentence
• In الغابة الكبيرة, the second word is an adjective directly modifying the noun

A very useful pattern to remember:

• definite noun + indefinite adjective/form → often a sentence: The noun is ...
• definite noun + definite adjective → a noun phrase: the ... noun

Not as the normal neutral equivalent of الغابة كبيرة.

The usual basic sentence is:

• الغابة كبيرة

Starting with كبيرة would be marked, poetic, or require a different structure and context. For a beginner, the safest standard pattern is:

• noun first
• description second

So for simple MSA sentences like this, use:

• الغابة كبيرة
• المدينة جميلة
• البيت واسع