היא אמרה שהילדים ישנים אצל חברים הלילה, ולכן הבית יהיה שקט.

Because the subject is היא = she. In the past tense, Hebrew verbs agree with the subject’s gender and number.

• אמרה = she said
• אמר = he said

So היא אמרה is the correct match.

ש means that in this sentence.

So:

• היא אמרה = she said
• שהילדים ישנים... = that the children are sleeping / staying over...

In Hebrew, this ש is attached directly to the next word, so ש + הילדים becomes שהילדים.

In Hebrew, ישנים already means sleep / are sleeping for a masculine plural subject.

English needs are sleeping, but Hebrew uses one word:

• ישן = sleeping (masculine singular)
• ישנה = sleeping (feminine singular)
• ישנים = sleeping (masculine plural)
• ישנות = sleeping (feminine plural)

So הילדים ישנים literally looks like the children sleeping, but it naturally means the children are sleeping.

Because הילדים is grammatically masculine plural.

Hebrew often uses the masculine plural form for:

• a group of boys
• a mixed group
• a group whose gender is unspecified

So even if English just says the children, Hebrew uses ישנים unless the group is specifically all female, in which case you would use ישנות.

Literally, ישנים means are sleeping. But in this context, with אצל חברים הלילה, it naturally means sleeping over / staying the night at friends’ place.

So the literal sense is still sleeping, but the full phrase gives it the idiomatic meaning of spending the night somewhere else.

אצל means something like at someone’s place, with, or by someone, depending on context.

In this sentence:

• אצל חברים = at friends’ place / with friends

It is very commonly used when talking about being at a person’s home or in someone’s care.

Examples:

• אני אצל דני = I’m at Danny’s place
• הילדים אצל סבתא = the children are at Grandma’s

Because חברים here is indefinite: at friends’ place, not at the friends’ place.

• אצל חברים = at friends’ / at some friends’ place
• אצל החברים = at the friends’ place / at those specific friends’ place

So the sentence is talking generally about friends, not necessarily a specific already-defined group.

Yes, literally הלילה is the night, but in normal Hebrew it often functions as the adverb tonight.

This is very common with time expressions. So in context:

• הלילה = tonight

You should learn it as a standard time word, not just as a literal noun phrase.

יהיה is the future tense of להיות = to be.

Here it agrees with הבית:

• הבית = the house / the home
• יהיה = will be

So:

• הבית יהיה שקט = the house will be quiet

Since בית is masculine singular, יהיה is masculine singular too.

Because שקט is an adjective agreeing with הבית, and בית is masculine singular.

So the adjective must also be masculine singular:

• בית שקט = a quiet house
• דירה שקטה = a quiet apartment

That is why the sentence uses שקט.

ולכן means and therefore, and so, or therefore.

It is made of:

• ו = and
• לכן = therefore

So it links the two ideas:

• the children are sleeping over at friends’ place tonight
• therefore the house will be quiet

It sounds a bit more formal or written than simple אז, but it is completely natural.

No, Hebrew word order is somewhat flexible, especially with time words like הלילה.

The original sentence is natural:

• שהילדים ישנים אצל חברים הלילה

But other orders are possible, for example:

• שהילדים הלילה ישנים אצל חברים
• שהלילה הילדים ישנים אצל חברים

These may shift emphasis slightly, but the basic meaning stays the same. The original version sounds smooth and standard.

It can mean either, depending on context.

In this sentence, הבית יהיה שקט most naturally means:

• the house will be quiet or
• the home will be quiet

English often prefers the house, but the Hebrew word בית can carry both the physical and the family-home sense.

Not here, because the sentence is talking about the future.

• הבית שקט = the house is quiet
• הבית יהיה שקט = the house will be quiet

So יהיה is necessary to show that the quietness is expected later, as a result of the children being away tonight.