Лікарняний є в медичній картці.

Because it originally is an adjective, but here it is being used as a noun. This is very common in Ukrainian.

So лікарняний literally has the form of an adjective, but in real usage it can mean something like:

• sick leave
• a sick note
• a medical certificate for sick leave

This is called substantivization: an adjective starts functioning like a noun.

In this sentence, лікарняний is in the nominative singular masculine form, because it is the subject of the sentence.

It can mean either, depending on context.

Commonly, лікарняний can refer to:

• the sick-leave document / certificate
• the time someone is officially on sick leave

In this sentence, because it says in the medical record/card, the meaning is much more likely the document / note / record of sick leave, not the time period itself.

So context tells you which meaning is intended.

Here є means is.

So grammatically, Лікарняний є в медичній картці = The sick note is in the medical record/card.

But in Ukrainian, the present-tense verb to be is often omitted, especially in simple statements.

So you may also hear:

• Лікарняний в медичній картці.

That is also understandable and natural in many contexts.

Using є can make the sentence sound a bit more explicit or formal. It is especially common when you want to clearly state existence or presence.

Because after в meaning in, when you are talking about location, Ukrainian normally uses the locative case.

The basic dictionary form is:

• медична картка = nominative

But after в for location, it changes to:

• в медичній картці = locative

Both words change because both the adjective and the noun must match the required case:

• медична → медичній
• картка → картці

So the form is not random; it is required by the grammar.

This is a normal Ukrainian case change.

The noun картка is feminine singular. In the locative singular, it becomes картці.

Two things happen:

1. the ending changes
2. the consonant к changes to ц before that ending

So:

• картка → картці

This kind of consonant change is very common in Ukrainian noun declension. You do not need to translate it literally; just learn it as the regular locative form of картка.

Because this sentence describes where something is, not movement into somewhere.

• в медичній картці = in the medical record → location, so locative
• в медичну картку = into the medical record/card → direction or movement, so accusative

Compare:

• Лікарняний є в медичній картці.
  The sick note is in the medical record.

• Лікар поклав лікарняний в медичну картку.
  The doctor put the sick note into the medical record.

So the case depends on whether the phrase shows location or destination.

Yes. Ukrainian word order is fairly flexible, and changing it often changes the focus or emphasis.

For example:

• Лікарняний є в медичній картці.
  Focuses more on лікарняний as the topic: the sick note is in the medical record.

• У медичній картці є лікарняний.
  Sounds more like There is a sick note in the medical record.
  This is a more clearly existential pattern.

So both are possible, but they do not sound exactly the same in emphasis.

Both в and у can mean in. Ukrainian often chooses between them for ease of pronunciation and smoother sound.

So:

• в медичній картці
• у медичній картці

are both possible in principle.

Speakers choose the one that sounds better next to the surrounding words. This is called euphony.

In your sentence, в медичній картці sounds perfectly natural.

It is in the nominative case.

That is because лікарняний is the subject of the sentence — it is the thing whose location is being stated.

So the sentence structure is roughly:

• лікарняний = subject, nominative
• є = is
• в медичній картці = prepositional phrase showing location

Even though лікарняний looks like an adjective, here it behaves like a noun in the nominative.