Между прочим, он как раз искал тот адрес, который ты записала в блокнот.

Между прочим is a set expression that often means by the way, incidentally, or as it happens.

In this sentence, it adds a conversational tone, as if the speaker is mentioning something relevant but slightly side information:

• Между прочим, ... = By the way, ...

Literally, the words mean something like among other things, but you should treat it as a fixed expression.

Как раз is a very common phrase with several related meanings, and here it means something like:

• just
• exactly
• right at that moment
• precisely

So он как раз искал... suggests:

• he was just looking for...
• he happened to be looking for...
• that was exactly what he was looking for at that moment

It gives a sense of coincidence or perfect timing.

Искал is the past tense imperfective form of искать (to look for / to search for).

The imperfective is used because the sentence focuses on the process of searching, not on completion or result.

• он искал = he was looking for / he looked for
• он нашёл = he found
• он поискал = he searched for a while

Here the point is not that he found the address, but that he was in the middle of looking for it. That is why искал is natural.

Тот адрес means that address or the address in question.

Russian often uses тот to point to a specific thing that both speaker and listener can identify, especially when it is followed by a relative clause:

• тот адрес, который... = that address which... / the address that...

In English, we often just say:

• the address you wrote down

But Russian commonly uses:

• тот + noun + который...

It helps clearly mark the noun being specified.

Который is a relative pronoun meaning which, that, or sometimes the one that.

It introduces the clause that describes адрес:

• тот адрес, который ты записала в блокнот
• the address that you wrote down in the notebook

So the structure is:

• тот адрес = that address
• который ты записала в блокнот = which/that you wrote down in the notebook

This is a very common Russian pattern.

Because который is the direct object of записала in the relative clause.

The verb записать takes a direct object:

• записать адрес = to write down an address

So the relative pronoun has to be in the accusative case. Since адрес is:

• masculine
• singular
• inanimate

the accusative form looks the same as the nominative:

• nominative: который
• accusative (masculine inanimate): который

If it were animate masculine, you would see a different form. For example:

• человек, которого я видел = the person whom I saw

But with an inanimate noun like адрес, accusative = nominative, so который is correct.

Because Russian past tense verbs agree in gender with the subject.

Here the subject is ты (you), and the speaker is addressing a female person, so:

• ты записала = you wrote down (said to a woman)

If the speaker were talking to a man, it would be:

• ты записал

This is one of the big differences from English: in the Russian past tense, the verb shows the gender of the person who did the action.

Записать usually means to write down, to note, or to make a written record of something.

So:

• писать = to write
• записать = to write down / note down

In this sentence, the idea is not just that you were writing in general, but that you specifically wrote down the address for future reference.

Also, записала is perfective, which fits the idea of a completed act:

• you successfully wrote the address down

Here в блокнот uses the accusative case, because the phrase suggests putting the information into the notebook.

• записать в блокнот = to write down into a notebook / in a notebook

This is the normal idiomatic expression with записать.

Compare:

• в блокнот = into the notebook / in the notebook as the destination of writing
• в блокноте = in the notebook, referring more to location

Russian often uses в + accusative when something is being directed into a place, even if English simply says in.

Not exactly.

• блокнот = notebook / notepad, often smaller, for notes
• тетрадь = exercise book / notebook, often the kind used in school

So в блокнот suggests a small notebook or notepad where someone jotted the address down.

The sentence breaks down like this:

• Между прочим, = By the way,
• он как раз искал = he was just looking for
• тот адрес, = that address
• который ты записала в блокнот. = that you wrote down in the notebook.

So literally, it is:

• By the way, he was just looking for that address which you wrote down in the notebook.

A more natural English version would be:

• By the way, he was just looking for the address you wrote down in your notebook.

Yes. Russian word order is fairly flexible, although the original version sounds natural and neutral.

Original:

• Между прочим, он как раз искал тот адрес, который ты записала в блокнот.

You could move things around for emphasis, for example:

• Он как раз искал, между прочим, тот адрес, который ты записала в блокнот.
• Тот адрес, который ты записала в блокнот, он как раз искал.

These versions change the emphasis or sound more marked. The original is the most straightforward conversational order.

By itself, адрес can mean different kinds of address:

• a street/postal address
• an email address
• a web address

Without more context, learners usually assume a physical address, especially because someone wrote it down in a notebook. But the word itself is broader than that.

You would change записала to записал:

• Между прочим, он как раз искал тот адрес, который ты записал в блокнот.

Everything else stays the same. The only change is the past tense verb agreeing with a male ты.