המפתח שלו בתוך התיק, לא בארנק.

In Hebrew, the present tense often leaves out the verb to be.

So המפתח שלו בתוך התיק literally looks like his key inside the bag, but it means His key is inside the bag.

This is very normal in Hebrew. In past or future, Hebrew would use a verb, but in the present it usually does not.

שלו means his.

Hebrew commonly shows possession with של + a pronoun:

• שלי = mine
• שלך = yours
• שלו = his
• שלה = hers

So:

• המפתח שלו = his key

This is a very common and natural way to express possession in modern Hebrew.

Hebrew also has possessive suffixes in some cases, but with a noun like מפתח, using שלו is the standard everyday form.

The normal word order is:

• noun first
• possessor after it

So:

• המפתח שלו = his key

Putting שלו first would sound unnatural here.

English says his key, but Hebrew usually says something closer to the key of his.

The ה־ is the Hebrew definite article, meaning the.

So:

• מפתח = a key / key
• המפתח = the key

In this sentence, המפתח שלו means his key, but Hebrew still often uses the definite article on the noun:

• המפתח שלו = literally the key of his

This is the normal Hebrew structure.

Actually, both places are definite in form.

• בתוך התיק = inside the bag
• בארנק = in the wallet

In בארנק, the preposition ב־ (in) is attached directly to הארנק (the wallet), and the ה changes shape in the combined form.

So:

• הארנק = the wallet
• ב + הארנק = בארנק = in the wallet

This is a common pattern in Hebrew:

• בבית = in the house
• בספר = in the book
• בארנק = in the wallet

Both can mean something like in the bag, but בתוך is more specifically inside.

So:

• בתוך התיק = inside the bag
• בתיק = in the bag

בתוך adds a stronger sense of physical interior location. It can sound a bit more explicit or emphatic.

In this sentence, בתוך התיק, לא בארנק clearly contrasts two places:

• inside the bag
• not in the wallet

Hebrew often leaves out repeated material when it is understood from context.

So:

• המפתח שלו בתוך התיק, לא בארנק means
• His key is inside the bag, not in the wallet

The full version could be something like:

• המפתח שלו בתוך התיק, לא בתוך הארנק or
• המפתח שלו בתוך התיק, הוא לא בארנק

But that would be less natural here. Hebrew, like English, often shortens this kind of contrast.

Yes, לא is the normal word for not.

Here it negates the location phrase:

• לא בארנק = not in the wallet

This is different from אין, which is used for there is not / there are not / do not have in other kinds of sentences.

For example:

• הוא לא בבית = He is not at home
• אין מפתח בתיק = There is no key in the bag

So in your sentence, לא is exactly the right choice.

The comma marks a pause and helps show the contrast:

• inside the bag, not in the wallet

It works a lot like English punctuation in a sentence such as:

• It’s in the bag, not in the wallet.

In speech, you would usually hear a slight pause before לא בארנק.

A common pronunciation would be:

ha-maf-TE-aḥ she-LO be-TOKH ha-TIK, lo ba-ar-NÁK

A few notes:

• מפתח is stressed on the last syllable: maf-TE-aḥ
• שלו is stressed on the end: she-LO
• בתוך is stressed on the second syllable: be-TOKH
• תיק is a one-syllable word: tik
• בארנק is usually pronounced ba-ar-NÁK

The sound ḥ in מפתח is the throaty Hebrew letter ח.

It normally refers to a specific key, because of ה־ in המפתח.

So this is not just a key of his in a vague sense. It is more like:

• his key
• the key belonging to him

In context, it usually means a particular key that both speaker and listener can identify.

Yes. מפתח can also mean things like opener or even index in some contexts.

But in this sentence, with inside the bag, not in the wallet, the natural meaning is definitely key.

Context makes that clear.