المحيط كبير.

الـ is the Arabic definite article, the same idea as the in English.

So:

• محيط = ocean
• المحيط = the ocean

In Egyptian Arabic, الـ is usually pronounced el- in normal speech, so المحيط is commonly pronounced something like el-moḥīṭ.

A simple learner-friendly pronunciation is:

el-moḥeet kibeer

A few sound notes:

• ح in المحيط is a breathy h sound made deeper in the throat than English h
• ee in moḥeet and kibeer is a long vowel, like the vowel in see
• ط is a heavier/emphatic t

If you want a slightly more careful transliteration, you could write it as:

el-muḥīṭ kibīr

In Arabic, present-tense sentences like X is big usually do not use a separate word for is.

So:

• المحيط كبير = the ocean is big

This is very normal in both Standard Arabic and Egyptian Arabic.

If you wanted past or future, then Arabic would use other forms, but in the simple present, the is is usually just understood.

In Arabic, descriptive words usually come after the noun they describe.

So:

• محيط كبير = a big ocean
• literally: ocean big

That is the normal Arabic order, even though English says big ocean.

In this sentence, كبير is functioning as the predicate of the sentence, but the same general idea still helps: Arabic often places the describing word after the noun.

Because كبير here is the predicate adjective in a full sentence:

• المحيط كبير = the ocean is big

In this kind of sentence, the adjective is normally indefinite, so it does not take الـ.

Compare:

• المحيط كبير = the ocean is big
• المحيط الكبير = the big ocean

So adding الـ to كبير changes it from a sentence into a noun phrase, or at least strongly suggests that reading.

Because المحيط is a masculine singular noun, and the adjective has to match it.

So:

• masculine singular: كبير
• feminine singular: كبيرة

Since المحيط is masculine, you say:

• المحيط كبير

If the noun were feminine, the adjective would usually change too.

It works in both.

• In Standard Arabic, it is completely normal.
• In Egyptian Arabic, people can also say it, especially since the words themselves are familiar.

The main difference in everyday Egyptian is usually pronunciation, not the basic structure here. An Egyptian speaker would typically pronounce it more like:

el-moḥeet kibeer

So the sentence is very learner-friendly because it matches both systems quite well.

In Egyptian Arabic, the easiest way is:

المحيط مش كبير el-moḥeet mish kibeer

This means:

• the ocean is not big

Here, مش is the common Egyptian word for not in this kind of sentence.

The difference is definiteness:

• المحيط كبير = the ocean is big
• محيط كبير = a big ocean

So:

• with الـ on the noun, you get the ocean
• without الـ, you get an ocean / a big ocean, depending on context

This is an important contrast in Arabic.

Yes. A common way is to add جداً after the adjective:

المحيط كبير جداً

This means:

• the ocean is very big

In Egyptian speech, people also often use other everyday intensifiers, but جداً is the straightforward form learners usually meet first.