Learn Hardcore Greek: Γράφω τις καινούριες εκφράσεις στο τετράδιό μου για να τις θυμάμαι. - I write the new expressions in my notebook so that I remember them.

Τις here is the definite article in the accusative feminine plural form, agreeing with εκφράσεις (expressions), which is also feminine plural accusative.

So:

τις = the (feminine, plural, accusative)
καινούριες = new (feminine, plural, accusative)
εκφράσεις = expressions (feminine, plural, accusative)

You need the article because in Greek, definite nouns almost always take the article, even when in English you might be tempted to drop “the”. Here it’s simply “the new expressions”.

Why is τις used again in για να τις θυμάμαι? Isn’t that repeating it?

The second τις is not an article this time; it is a weak object pronoun meaning “them”.

First τις: the article — τις καινούριες εκφράσεις = the new expressions
Second τις: pronoun — για να τις θυμάμαι = so that I remember them

Greek often repeats the reference with a pronoun even when the noun has just been mentioned. English normally avoids that repetition, but in Greek it’s very natural and often preferred.

Could I omit the second τις and just say για να θυμάμαι?

You can say για να θυμάμαι if the context already makes it 100% clear what you’re talking about. It would mean “so that I remember (them/it)”, with the object just understood.

However, in a neutral sentence like this, Greeks normally include the object pronoun:

για να τις θυμάμαι sounds complete and natural.
για να θυμάμαι can sound a bit unfinished unless the object is very obvious from context.

So the version with τις is the standard, natural wording here.

What tense or aspect is γράφω here, and does it mean “I write” or “I am writing”?

Γράφω is the present tense of the verb “to write”. In modern Greek, the present tense usually covers both:

I write (habitually)
I am writing (right now)

In this sentence, it most naturally means something habitual:
“I write the new expressions in my notebook so that I remember them.”

If you wanted to refer to a specific past action, you would use the aorist:

Έγραψα τις καινούριες εκφράσεις στο τετράδιό μου… = I wrote the new expressions in my notebook…

Why is it στο τετράδιό μου and not σε το τετράδιο μου?

Στο is a contraction of:

σε (in, at, on) + το (the, neuter singular) → στο

So:

σε το τετράδιο μου → στο τετράδιό μου

This kind of contraction is very common:

σε + τον → στον (στον φίλο μου)
σε + την → στη(ν) (στη φίλη μου)
σε + τους → στους (στους φίλους μου)

So στο τετράδιό μου literally = “in the notebook of mine”, i.e. “in my notebook.”

Why does τετράδιό have an accent on the last syllable as well — τετράδιό μου? Isn’t each word supposed to have only one accent?

On its own, the word is τετράδιο (with one accent on -τρά-).

When you add the enclitic (unstressed) pronoun μου, Greek accent rules allow a second accent on the last syllable:

τετράδιο → τετράδιό μου

This happens because τετράδιο is stressed on the antepenultimate syllable (third from the end). When such a word takes an enclitic (μου, σου, του, της, μας, σας, τους), a second accent is added on the last syllable to keep the stress pattern legal in Greek.

You’ll see the same pattern with other words:

δάσκαλος → δάσκαλός μου (my teacher)
άνθρωπος → άνθρωπός μου (my person)

So τετράδιό μου is correct and not a typo.

What exactly does για να mean here? Is it the same as “to” or “in order to”?

Για να introduces a purpose clause and is usually translated as “in order to” or simply “to” in English:

Γράφω… για να τις θυμάμαι.
→ I write… *in order to remember them.*

Grammatically, να triggers the subjunctive mood in Greek, and θυμάμαι here is in the present subjunctive (which looks the same as the present indicative for this verb).

So the structure is:

για να
- subjunctive = in order to + verb

What kind of verb is θυμάμαι? It looks reflexive – literally “I remember myself”?

Θυμάμαι is a so‑called middle/passive form, but in modern Greek it functions as an ordinary active verb meaning “to remember”.

So:

θυμάμαι = I remember
It is not used with a direct reflexive meaning like “I remember myself.”

Compare:

θυμάμαι τις εκφράσεις = I remember the expressions.
δεν τις θυμάμαι = I don’t remember them.

It belongs to a group of verbs that look passive in form (ending in -άμαι, -ούμαι, -ιέμαι, etc.) but have active meanings.

Why is the object pronoun τις placed before the verb in για να τις θυμάμαι? Could it go after the verb?

In normal statements and questions, Greek weak object pronouns (με, σε, τον, την, το, μας, σας, τους, τις, τα) usually go before the verb:

Τις θυμάμαι. = I remember them.
Για να τις θυμάμαι. = In order to remember them.

They go after the verb mainly in:

affirmative imperatives: θυμήσου τις! (remember them!)
some fixed phrases and participle-like forms.

So in this sentence, τις θυμάμαι (not θυμάμαι τις) is the standard clitic placement when using only the pronoun.

What is the difference between καινούριες and νέες? Could I say νέες εκφράσεις instead?

You can say νέες εκφράσεις; it’s grammatically correct and understandable.

Nuance:

καινούριος / καινούρια / καινούριο: emphasizes newness as “brand‑new, unused, just acquired”.
νέος / νέα / νέο: broader “new, recent”, also used for “young” (for people).

In many contexts they overlap, but:

καινούριες εκφράσεις suggests new (to me) expressions I’ve just learned or encountered.
νέες εκφράσεις could mean new in general, possibly recently coined or new in the language, depending on context.

In everyday speech about things you’re just learning, καινούριες εκφράσεις feels very natural.

What case are τις καινούριες εκφράσεις in, and why that case?

They are in the accusative case, feminine plural:

τις (article, fem. pl. acc.)
καινούριες (adjective, fem. pl. acc.)
εκφράσεις (noun, fem. pl. acc.)

The accusative is used here because τις καινούριες εκφράσεις is the direct object of γράφω:

Γράφω (τι;) τις καινούριες εκφράσεις.
→ I write (what?) the new expressions.

What exactly does μου mean in το τετράδιό μου? Is it the same as “my” in English?

Μου is an unstressed (enclitic) possessive pronoun meaning “my” or “of me”.

το τετράδιό μου = my notebook / the notebook of mine

Unlike English, Greek doesn’t use a separate possessive adjective like “my”. Instead, it uses the definite article + noun + μου:

το βιβλίο μου = my book
η τσάντα μου = my bag
οι φίλοι μου = my friends

When you want to emphasize the ownership, you can use a stressed form:

το δικό μου τετράδιο = my notebook (as opposed to someone else’s).

Could I say για να τις θυμηθώ instead of για να τις θυμάμαι? What is the difference?

Yes, you can say για να τις θυμηθώ, but it changes the aspect and therefore the meaning:

θυμάμαι (present) → ongoing state, habit, or repeated action:
- για να τις θυμάμαι = so that I (can) remember them / keep them in mind (over time).
θυμηθώ (aorist subjunctive) → a single, completed act of remembering:
- για να τις θυμηθώ = so that I (will) remember them (at some specific moment).

In your original sentence, the idea is to keep the expressions in memory generally, so για να τις θυμάμαι is the most natural choice.