כשהספרנית הקבועה לא הייתה שם, ספרנית אחרת עזרה לי למצוא את הספר שביקשתי.

כשהספרנית means when the librarian.

Here, כש־ is a conjunction meaning when. It attaches directly to the next word:

• כש־ = when
• הספרנית = the librarian

So:

• כשהספרנית הקבועה לא הייתה שם = when the regular librarian wasn’t there

This is very common in Hebrew: short function words often attach to the following word.

Because ספרנית is the feminine form of librarian, while ספרן is the masculine form.

In this sentence, the librarian is grammatically feminine, so the related words also appear in feminine form:

• ספרנית
• הקבועה
• הייתה
• אחרת
• עזרה

If the sentence were about a male librarian, you would expect forms like:

• ספרן
• הקבוע
• היה
• אחר
• עזר

Because הספרנית הקבועה means the regular librarian, which is definite.

In Hebrew, when a noun is definite, the adjective describing it is usually definite too.

So:

• ספרנית קבועה = a regular librarian
• הספרנית הקבועה = the regular librarian

This is a very important pattern in Hebrew:

• noun + adjective
• if the noun has ה־, the adjective usually also has ה־

Examples:

• הספר הגדול = the big book
• ילדה חכמה = a smart girl
• הילדה החכמה = the smart girl

All of those are related, and the best translation depends on context.

The adjective קבוע / קבועה can mean:

• fixed
• permanent
• regular

In this sentence, הספרנית הקבועה most naturally means the regular librarian or the usual librarian.

So it is probably referring to the librarian who is normally there.

לא הייתה שם means was not there.

Breakdown:

• לא = not
• הייתה = she was
• שם = there

So literally:

• לא הייתה שם = she was not there

This is standard Hebrew past-tense negation:

• לא
  • past-tense verb

Examples:

• לא ידעתי = I didn’t know
• לא ראינו = we didn’t see
• לא הייתה = she wasn’t

Yes, שם can mean either there or name. The meaning depends on context.

In this sentence:

• לא הייתה שם = she wasn’t there

But in another sentence:

• מה השם שלך? = what is your name?

This is a very common Hebrew word with two meanings, and context usually makes it clear.

Because ספרנית אחרת means another librarian, which is indefinite.

Compare:

• ספרנית אחרת = another librarian / a different librarian
• הספרנית האחרת = the other librarian

So in your sentence, the speaker is not referring to one specifically identified other librarian, but simply another librarian.

Also notice adjective agreement again:

• ספרנית = feminine singular noun
• אחרת = feminine singular adjective

Because its subject is ספרנית אחרת, which is feminine singular.

Hebrew past-tense verbs agree with the subject in gender and number.

So:

• עזרה = she helped
• עזר = he helped
• עזרו = they helped

Since ספרנית is feminine singular, עזרה is the correct form.

לי means to me.

So:

• עזרה לי = helped me

The verb עזר often takes an indirect object with ל־ in modern Hebrew:

• הוא עזר לי = he helped me
• היא עזרה לו = she helped him
• עזרנו להם = we helped them

So even though English says simply helped me, Hebrew commonly uses helped to me structurally.

למצוא means to find.

The ל־ is the usual marker for the infinitive in Hebrew, similar to English to:

• לראות = to see
• ללכת = to go
• לקרוא = to read
• למצוא = to find

So:

• עזרה לי למצוא = helped me find / helped me to find

That is a very common structure after another verb.

Here את is the direct object marker. It has no English equivalent.

Hebrew uses את before a definite direct object, usually one with ה־ or a possessive/reference that makes it definite.

So:

• מצאתי ספר = I found a book
• מצאתי את הספר = I found the book

In your sentence:

• את הספר = the book, as the direct object of למצוא

This is one of the most important particles in Hebrew.

שביקשתי means that I asked for or more literally that I requested.

It is made of:

• ש־ = that / which
• ביקשתי = I requested / I asked for

So:

• הספר שביקשתי = the book that I asked for

This is a relative clause, like English the book that...

A useful point: Hebrew לבקש can often work where English uses ask for.

So although English says:

• the book that I asked for

Hebrew can say more literally:

• the book that I requested

Modern Hebrew often uses subject–verb order, especially in ordinary spoken and written sentences.

So:

• ספרנית אחרת עזרה לי = another librarian helped me

This is very natural.

Hebrew can also use verb-first order in some contexts, but the order here is straightforward and common, especially after the opening time clause.

The sentence structure is:

• כשהספרנית הקבועה לא הייתה שם = when the regular librarian wasn’t there
• ספרנית אחרת עזרה לי למצוא את הספר שביקשתי = another librarian helped me find the book I asked for

So the whole sentence flows as:

• time/background first
• main event second

The comma separates the opening subordinate clause from the main clause.

So:

• כשהספרנית הקבועה לא הייתה שם = dependent clause
• ספרנית אחרת עזרה לי למצוא את הספר שביקשתי = main clause

This is similar to English punctuation in a sentence like:

• When the regular librarian wasn’t there, another librarian helped me...

So the comma is doing basically the same job it does in English.