אני לא יודעת האם הוא כבר בבית.

Because יודעת is the feminine singular form.

In Hebrew, the present-tense form usually agrees with the gender and number of the subject. Since the speaker is אני = I, and the form is יודעת, this tells you the speaker is female.

• אני לא יודעת = a woman saying I don't know
• אני לא יודע = a man saying I don't know

So this sentence is specifically being said by a female speaker.

A male speaker would say:

אני לא יודע האם הוא כבר בבית.

The only change is:

• יודעת → יודע

Everything else stays the same.

האם means whether or if.

In this sentence, it introduces an indirect yes/no question:

• אני לא יודעת האם הוא כבר בבית.
• I don't know whether / if he is already home.

So האם is not the question word what or is? It is a connector meaning whether.

Both can mean whether / if, but they are used a little differently.

• האם is more formal, clearer, and very common in writing or careful speech.
• אם is also used for whether, especially in everyday language.

So these are both possible:

• אני לא יודעת האם הוא כבר בבית.
• אני לא יודעת אם הוא כבר בבית.

Both are correct. In many everyday conversations, אם sounds more natural and common.

One important note: אם can also mean if in conditional sentences, like if it rains. So האם can sometimes help avoid ambiguity.

Because לא is the normal Hebrew word for not, and it usually comes before the word or phrase being negated.

Here it negates יודעת:

• אני יודעת = I know
• אני לא יודעת = I do not know / I don't know

This is the normal Hebrew word order for negation.

Hebrew usually does not use a separate present-tense verb to be in sentences like this.

So:

• הוא בבית literally looks like he at home
• but it means he is at home

Also:

• אני לא יודעת literally looks like I not knowing / knowing-feminine
• but it means I don't know

This is very normal in Hebrew. In the present tense, Hebrew often leaves out is / am / are.

Sometimes Hebrew can leave out the subject, but not as freely as some other languages.

In the present tense, forms like יודע / יודעת / יודעים / יודעות show gender and number, but usually not person clearly enough. Because of that, speakers often include אני, הוא, היא, etc., especially for clarity.

So:

• אני לא יודעת = very normal
• לא יודעת = also possible in conversation if the subject is obvious from context

In this sentence, using אני makes it clear that the speaker is the one who does not know.

Because Hebrew normally states the subject of the clause, especially when it is not obvious from context.

• הוא כבר בבית = he is already at home

Without הוא, the sentence would usually sound incomplete or too dependent on context.

So הוא is there simply because the clause needs the subject he.

כבר means already.

So:

• הוא כבר בבית = he is already at home

Its position here is very natural in Hebrew: after the subject and before the location.

This placement is similar to English:

• he already is home / more naturally he is already home

Hebrew word order can sometimes vary a bit, but הוא כבר בבית is a very standard and natural order.

בבית means in the house or, more naturally in many contexts, at home.

It is made of:

• ב־ = in / at
• בית = house / home

So:

• בבית = in the house / at home

In this sentence, the natural English meaning is usually at home.

Because Hebrew often attaches short prepositions directly to the following word.

The preposition ב־ (in / at) is one of these attached prepositions.

So instead of writing:

• ב הבית

Hebrew combines them into:

• בבית

This is the normal Hebrew spelling and form.

Also, when ב־ joins a noun with the article, Hebrew does not keep a separate visible ה in the same way English does. So בבית can mean in a house or in the house / at home, depending on context.

It is grammatically normal in both, but it sounds a bit more formal because of האם.

• With האם: slightly more formal or written style
• With אם: more everyday conversational style

So:

• אני לא יודעת האם הוא כבר בבית. = correct, a bit more formal
• אני לא יודעת אם הוא כבר בבית. = correct, very common in speech

A little, yes, but the given version is the safest and most neutral.

Standard order here is:

• אני לא יודעת האם הוא כבר בבית.

You may also hear small variations in speech, but changing the order can affect emphasis or sound less natural.

For a learner, this is a very good basic pattern to remember:

• [subject] + לא + [present-tense verb] + האם/אם + [subject] + כבר + [place]

So this sentence is a strong model for building similar ones.