Diagnosta już czeka.

Because in Polish, some masculine nouns for people end in -a. Diagnosta is one of them.

So even though it looks like many feminine nouns, it is typically treated as masculine in grammar:

• ten diagnosta = this diagnostician / this male diagnostician
• dobry diagnosta = a good diagnostician
• Diagnosta czekał = The diagnostician was waiting

A learner often expects -a to mean feminine, but Polish has a small group of masculine-person nouns like this.

It is in the nominative case because it is the subject of the sentence — the person doing the action.

So in Diagnosta już czeka, the structure is basically:

• Diagnosta = subject
• już = already
• czeka = is waiting / waits

Polish does not have articles like English the and a/an.

So diagnosta can mean:

• the diagnostician
• a diagnostician

Which one sounds best depends on the context. Polish usually leaves that to the situation, not to a separate word.

Here już means already.

It gives the idea that the waiting has begun by this point:

• Diagnosta czeka = The diagnostician is waiting.
• Diagnosta już czeka = The diagnostician is already waiting.

In context, już can sometimes also feel like by now or now already, depending on tone.

In Polish, the simple present tense often covers both:

• waits
• is waiting

So czeka can mean either:

• waits
• is waiting

In this sentence, English usually prefers is waiting, because it sounds like something happening right now.

Czeka comes from the infinitive czekać = to wait.

Czeka is the 3rd person singular present tense form, so it can mean:

• he waits / is waiting
• she waits / is waiting
• it waits / is waiting

Here it matches diagnosta, which is a singular subject.

Also, czekać is an imperfective verb, which is the normal choice for an ongoing action like waiting.

Polish often leaves out subject pronouns when they are not needed.

In this sentence, the subject is already stated as diagnosta, so there is no need to add on (he).

English:

• He is already waiting.

Polish:

• On już czeka.
  or
• Diagnosta już czeka.

The second version is perfectly natural because the noun itself tells you who is doing the action.

Yes. Polish word order is more flexible than English word order.

All of these are possible:

• Diagnosta już czeka.
• Już czeka diagnosta.
• Diagnosta czeka już.

But they do not sound exactly the same in emphasis.

The original Diagnosta już czeka is a neutral, natural way to say it.

Very roughly:

• Diagnosta już czeka = neutral statement
• Już czeka diagnosta = stronger focus on already or on the fact that the diagnostician is the one waiting
• Diagnosta czeka już = possible, but less neutral in many contexts

Czekać can stand alone, as in this sentence:

• Diagnosta już czeka. = The diagnostician is already waiting.

If you want to say who/what someone is waiting for, Polish usually uses na + accusative:

• Diagnosta już czeka na pacjenta. = The diagnostician is already waiting for the patient.
• Diagnosta już na ciebie czeka. = The diagnostician is already waiting for you.

So the sentence is complete as it is, but you can add more information if needed.

A rough English-friendly pronunciation is:

dya-GNOS-ta yoosh CHE-ka

A few sound notes:

• ż in już sounds like the s in measure
• cz in czeka sounds like ch in chop
• stress in Polish usually falls on the second-to-last syllable, so:
  • diaGNOSta
  • CZEka

So the rhythm is: dya-GNOS-ta yoosh CHE-ka