Learn Hardcore Greek: Ο φύλακας της παιδικής χαράς είναι πια γνωστός μου, αλλά για τα παιδιά είμαι ακόμα άγνωστος. - The playground guard is now an acquaintance of mine, but for the children I am still a stranger.

Ο φύλακας της παιδικής χαράς = the guard of the playground.
Greek often uses the genitive to show possession or association, where English might use of or an ’s.

So:

ο φύλακας = the guard (nominative, subject)
της παιδικής χαράς = of the playground (genitive, dependent on φύλακας)

Why are both παιδικής and χαράς in the genitive?

Because παιδικής is an adjective modifying χαράς, so it must agree with that noun in:

gender (feminine),
number (singular),
case (genitive).

Base forms:

παιδική χαρά = playground (lit. “children’s joy”)
In the genitive:
- παιδική → παιδικής (fem. gen. sg.)
- χαρά → χαράς (fem. gen. sg.)

So της παιδικής χαράς is the fully inflected phrase.

What is the function and nuance of πια in είναι πια γνωστός μου?

Πια is an adverb meaning roughly “now / by now / anymore”. Here it gives the sense of a change over time:

είναι γνωστός μου = he is known to me / he is an acquaintance of mine
είναι πια γνωστός μου = he is now known to me / he has by now become known to me

So the sentence implies that previously he was unknown to me, but that has changed.

What is the difference between πια and ακόμα in this sentence?

They both relate to time, but they work differently:

πια (in positive sentences) → “now, by now”, often implying a change has already happened.
- είναι πια γνωστός μου = he is now known to me (he didn’t use to be).
ακόμα (or ακόμη) → “still, yet”, implying an ongoing state that has not changed yet.
- είμαι ακόμα άγνωστος = I am still unknown.

Together, they nicely contrast:

The guard’s status has changed for me (πια).
My status has not yet changed for the children (ακόμα).

Why is it γνωστός μου and not something like γνωστός σε μένα?

In Greek, adjectives like γνωστός (“known”) often take a genitive pronoun instead of a prepositional phrase:

είναι γνωστός μου = he is known to me / he is an acquaintance of mine
είναι γνωστός σου = he is known to you
είναι γνωστός μας = he is known to us

You can say είναι γνωστός σε μένα (or σε εμένα), and it is correct, but:

γνωστός μου is shorter, very natural, and slightly more idiomatic in this context.
σε μένα adds emphasis to me (e.g. “to me (as opposed to others)”).

So the genitive clitic (μου) is the normal, neutral choice here.

What is the difference between είναι γνωστός μου and something like με ξέρει?

They focus on different directions of knowing:

είναι γνωστός μου
- Literally: “he is known to me”.
- Emphasis: I know him; he is an acquaintance of mine.
- Common translation: “he is an acquaintance of mine / I know him.”
με ξέρει = “he knows me”
- Subject: he
- Object: me

So:

είναι γνωστός μου: from my perspective – I am familiar with him.
με ξέρει: from his perspective – he is familiar with me.

Why is it γνωστός and άγνωστος (masculine), and how would this change if the speaker were female?

Adjectives in Greek agree in gender, number, and case with the noun or implied subject.

In είναι πια γνωστός μου, the subject is ο φύλακας (masculine singular), so:
- γνωστός = masc. nom. sing.
In είμαι ακόμα άγνωστος, the implied subject is εγώ.
If the speaker is assumed to be male, άγνωστος (masc. nom. sing.) is used.

If the speaker were female, she would say:

είμαι ακόμα άγνωστη (“I am still unknown” – said by a woman).

Similarly, if the subject changed, the adjective would change:

η φύλακας (female guard) → Η φύλακας είναι πια γνωστή μου.

Why does the second clause start with για τα παιδιά? Would Είμαι ακόμα άγνωστος για τα παιδιά also be correct?

Yes, Είμαι ακόμα άγνωστος για τα παιδιά is grammatically correct and natural.

Placing για τα παιδιά at the beginning, as in:

Αλλά για τα παιδιά είμαι ακόμα άγνωστος.

does two things:

Topicalization / emphasis: It highlights “as far as the children are concerned” – putting them in focus.
Keeps the contrast clear:
- For me: he is now known.
- For the children: I am still unknown.

Greek word order is flexible; fronting για τα παιδιά is mainly about emphasis and rhythm, not grammar.

Why is it για τα παιδιά and not something like στα παιδιά?

Both can be used, but they have slightly different feels:

για τα παιδιά (for/to the children, as far as the children are concerned)
- More general: “in the eyes of the children”, “from the children’s point of view”.
- Very natural for this “from their perspective” meaning.
στα παιδιά (to the children, literally “at/to the children”)
- Often used like English “to”:
  - είμαι γνωστός στα παιδιά = I am known to the children.

In your sentence, για τα παιδιά είμαι ακόμα άγνωστος strongly suggests:
“From the children’s point of view, I am still unknown.”
So για is a good choice for that nuance of “as far as they’re concerned”.

Why is there no explicit “I” (εγώ) in είμαι ακόμα άγνωστος?

In Greek, subject pronouns (εγώ, εσύ, αυτός, etc.) are often dropped because the verb ending already shows the person:

είμαι = I am
είσαι = you are
είναι = he/she/it is

So είμαι ακόμα άγνωστος clearly means “I am still unknown” without needing εγώ.

You would add εγώ only for emphasis or contrast, for example:

Εγώ είμαι ακόμα άγνωστος, αλλά ο φύλακας είναι πια γνωστός μου.
= I am still unknown, but the guard is now known to me.

Why is the present tense used (είναι, είμαι) when in English I might say “has become known” or “I remain unknown”?

Greek often uses the present tense where English might choose a more aspectual form (like the present perfect).

είναι πια γνωστός μου
Literally: “he is now known to me.”
Context adds the idea that this is a new state, i.e. “he has become known by now.”
είμαι ακόμα άγνωστος
Literally: “I am still unknown.”
English might say “I remain unknown”, but the basic state is just present.

So the straightforward Greek present covers both:

current state, and
implied recent change (helped by adverbs πια and ακόμα).

Why is it Ο φύλακας with an article? Could we drop Ο like in English?

In Greek, the definite article (ο, η, το) is used more regularly than in English, especially with occupations, roles, and specific people:

Ο φύλακας της παιδικής χαράς
= the specific guard of that playground.

If you dropped the article (Φύλακας της παιδικής χαράς είναι…), it would sound unusual or stylistically marked in this everyday context. In most normal sentences, you keep Ο here.

Does παιδική χαρά always mean “playground”? It looks like “children’s joy”.

Yes, παιδική χαρά is a fixed expression in Modern Greek meaning “playground”.

Literally:

παιδική = child(ish), children’s
χαρά = joy

Historically/semantically, it’s “children’s joy”, but in current usage:

πάμε στην παιδική χαρά; = “shall we go to the playground?”
ο φύλακας της παιδικής χαράς = the playground’s guard.

So you should learn παιδική χαρά as the normal phrase for playground.