זאת ודאי הכתובת הנכונה.

זאת is the feminine singular demonstrative, meaning this or sometimes that, depending on context.

In this sentence, it points to something being identified:
זאת ודאי הכתובת הנכונה = This is certainly the correct address.

So זאת is functioning like English this in This is the correct address.

A learner should also know that in modern Hebrew, זו is very common instead of זאת, especially in speech. So you may also hear:

זו ודאי הכתובת הנכונה

with basically the same meaning.

Because Hebrew normally leaves out the verb to be in the present tense.

So where English says:

• This is the correct address

Hebrew often simply says:

• זאת הכתובת הנכונה

That kind of sentence is called a nominal sentence: no present-tense is/am/are appears.

However, in the past or future, Hebrew does use forms of to be:

• זאת הייתה הכתובת הנכונה = This was the correct address
• זאת תהיה הכתובת הנכונה = This will be the correct address

ודאי means certainly, surely, or definitely.

Here it adds confidence or certainty to the statement:

• זאת הכתובת הנכונה = This is the correct address
• זאת ודאי הכתובת הנכונה = This is certainly the correct address

It is a fairly neutral word and can sound a bit more formal than very colloquial alternatives.

A related point: you may also see or hear forms like:

• בוודאי = certainly / of course
• בטח = sure / definitely in informal speech

But ודאי works very naturally in a sentence like this.

Because in Hebrew, when a noun is definite, its adjective must also be definite.

So:

• כתובת נכונה = a correct address
• הכתובת הנכונה = the correct address

This is a very important Hebrew pattern:

• ספר טוב = a good book
• הספר הטוב = the good book

So in your sentence, הכתובת הנכונה is one definite noun phrase: the correct address.

Because it has to agree with כתובת, which is a feminine singular noun.

Hebrew adjectives agree with the noun in:

• gender
• number
• definiteness

So:

• כתובת נכונה = feminine singular
• מכתב נכון = masculine singular
• כתובות נכונות = feminine plural
• מכתבים נכונים = masculine plural

Since כתובת is feminine singular, the adjective must be נכונה.

Yes, כתובת is feminine.

One clue is its ending: many feminine nouns end in ־ת, though not all nouns with that ending are feminine and not all feminine nouns have that ending. So this is a useful pattern, but not a perfect rule.

In practice, you learn the noun together with its gender. Since כתובת is feminine, anything agreeing with it will also be feminine:

• כתובת נכונה
• הכתובת הזאת
• כתובת חדשה

Both are feminine singular demonstratives meaning this.

In many contexts, they are interchangeable:

• זאת הכתובת הנכונה
• זו הכתובת הנכונה

In modern spoken Hebrew, זו is often more common.
זאת may sound a bit more formal, careful, or emphatic, though it is still completely normal and common.

So for a learner, the safest takeaway is:

• learn both
• recognize both
• expect to hear זו very often in conversation

The structure is:

זאת + ודאי + הכתובת הנכונה

or, in grammatical terms:

demonstrative + adverb + predicate noun phrase

Hebrew word order is somewhat flexible, but this order is very natural.

The core statement is:

• זאת הכתובת הנכונה

Adding ודאי before the noun phrase gives:

• זאת ודאי הכתובת הנכונה

That placement makes ודאי modify the whole statement in a natural way: this is certainly the correct address.

Yes. זוהי is a common written form meaning roughly this is for feminine singular.

So you might see:

• זוהי הכתובת הנכונה

This is especially common in writing and in slightly more formal styles.

Compare:

• זאת הכתובת הנכונה — very normal
• זו הכתובת הנכונה — very common, especially in speech
• זוהי הכתובת הנכונה — common in writing / somewhat more formal

All are useful to recognize.

A simple pronunciation guide would be:

zot va-DAI ha-kto-vet ha-ne-kho-NA

A few helpful notes:

• זאת = zot
• ודאי = vadai, with stress on the last syllable: va-DAI
• כתובת = ktovet or k'tovet
• נכונה = nekhoná / nekhona, with stress at the end

A full transliteration could be:

Zot vadai ha-ketovet ha-nekhona

Different transliteration systems may spell this slightly differently, but that is the general pronunciation.

Yes. Hebrew נכון / נכונה can mean correct, right, or appropriate, depending on context.

So הכתובת הנכונה can naturally be understood as:

• the correct address
• the right address

In English, right is often the most natural translation in everyday speech, while correct sounds a bit more explicit. Hebrew נכונה comfortably covers that idea.

You would replace ודאי with a word expressing probability, such as כנראה:

• זאת כנראה הכתובת הנכונה

That means This is probably / apparently the correct address.

This is useful because it shows how the sentence pattern stays the same:

• זאת ודאי הכתובת הנכונה = certainty
• זאת כנראה הכתובת הנכונה = probability

So once you know the structure, you can swap in other adverbs easily.