כדאי שלא נשאיר את האופניים בחצר, כי בלילה החצר חשוכה.

Here כדאי means it’s advisable, it’s a good idea, or it’s better.

So כדאי שלא נשאיר... means something like:

• We’d better not leave...
• It’s better not to leave...
• It’s advisable that we not leave...

In this sentence, כדאי is being used impersonally, not as a normal action verb.

שלא is made of:

• ש = that
• לא = not

So כדאי שלא נשאיר literally means It’s advisable that we not leave.

Hebrew often uses this pattern when giving advice about not doing something.

A very common alternative is:

• לא כדאי להשאיר את האופניים בחצר = It’s not a good idea to leave the bicycles in the yard

Both are natural. Very roughly:

• כדאי שלא נשאיר focuses on the recommended action: we should not leave them
• לא כדאי להשאיר focuses on the bad idea of leaving them

נשאיר is:

• future tense
• first person plural
• from the verb להשאיר = to leave something behind / to leave something somewhere

So literally נשאיר means we will leave.

But after words like כדאי, future forms are often translated more naturally in English as:

• we should leave
• we leave
• we not leave

depending on context.

Here it means we should not leave.

It is from להשאיר, not להישאר.

These two verbs are easy to confuse:

• להשאיר = to leave something
• להישאר = to stay / remain

In this sentence, we have a direct object:

• את האופניים = the bicycles

That shows the verb must be להשאיר, because you are leaving something.

Compare:

• נשאיר את האופניים בחצר = We’ll leave the bicycles in the yard
• נישאר בחצר = We’ll stay in the yard

את is the direct object marker.

Hebrew uses את before a definite direct object. Since האופניים means the bicycles, it is definite, so את is required.

So:

• נשאיר אופניים = we’ll leave bicycles / some bicycles
• נשאיר את האופניים = we’ll leave the bicycles

Important: את usually is not translated into English.

Because אופניים is one of those Hebrew nouns that normally appear in a plural/dual form even when talking about a single item.

It works a bit like English words such as:

• scissors
• glasses

So in everyday Hebrew, one bicycle is still אופניים.

That is why you will also see plural agreement with adjectives:

• אופניים חדשים = a new bicycle / new bicycles

Learners often expect a simple singular form, but in normal modern Hebrew, אופניים is the standard word.

Because Hebrew prepositions like ב, כ, and ל combine with the definite article ה.

So:

• ב + החצר becomes בחצר

This is very common.

So בחצר can mean:

• in the yard if it is definite
• in a yard if it is indefinite

In unpointed Hebrew, those look the same in writing. Context tells you which one is meant.

With vowels, they would be different:

• בַּחָצֵר = in the yard
• בְּחָצֵר = in a yard

Here, the meaning is clearly in the yard.

בלילה means at night or during the night.

It also contains the preposition ב = in/at, combined with the article:

• ב + הלילה → בלילה

So it is the same kind of contraction you saw in בחצר.

This expression is very common in Hebrew:

• ביום = in the daytime / by day
• בלילה = at night

Even though English usually says at night without the, Hebrew often uses the article in these fixed time expressions.

There is no separate word for is in a normal present-tense Hebrew sentence like this.

So:

• החצר חשוכה literally looks like the yard dark
• but it means the yard is dark

This is completely normal in Hebrew.

Compare:

• החצר חשוכה = The yard is dark
• החצר הייתה חשוכה = The yard was dark
• החצר תהיה חשוכה = The yard will be dark

So Hebrew omits is/am/are in the present tense, but uses forms of to be in the past and future.

Because חשוכה has to agree with החצר.

חצר is a feminine singular noun, so the adjective must also be feminine singular:

• חצר חשוכה = a dark yard
• החצר חשוכה = the yard is dark

Compare the masculine form:

• חדר חשוך = a dark room

So:

• חשוך = masculine singular
• חשוכה = feminine singular

Hebrew word order is more flexible than English.

Starting with בלילה puts the time first:

• בלילה החצר חשוכה = At night, the yard is dark

That sounds very natural in Hebrew, especially when setting the scene or explaining a reason.

You could also say:

• כי החצר חשוכה בלילה

That is also grammatical and natural. The difference is mostly one of emphasis and flow, not basic meaning.