Moje ruka je na rameni.

Moje is the possessive pronoun my, and it has to agree with the noun it describes.

Here, ruka is:

• feminine
• singular
• nominative (because it is the subject)

So moje is the correct agreeing form.

A useful note: Czech also has the shorter possessive form má. So Má ruka je na rameni is also possible.
The version with moje often sounds a bit more emphatic, contrastive, or simply fuller in style.

Ruka is in the nominative case.

Why? Because it is the subject of the sentence — the thing that is somewhere.

In Moje ruka je na rameni:

• Moje ruka = the subject
• je = is
• na rameni = the location phrase

So the noun naming the subject stays in the nominative.

Because na can take different cases depending on the meaning:

• na + accusative = movement onto something
• na + locative = position on something

Here the sentence describes location, not motion:

• the hand is on the shoulder

So Czech uses na + locative.

The noun rameno becomes rameni in the locative singular:

• nominative: rameno
• locative: rameni

So:

• na rameno = onto the shoulder
• na rameni = on the shoulder

Rameno is a neuter noun.

Yes, that matters, because gender affects how the noun changes in different cases.

For example:

• nominative singular: rameno
• locative singular: rameni

So the form rameni is partly there because:

1. the preposition na requires the locative for location
2. rameno is a neuter noun with this declension pattern

It can mean either, depending on context.

Czech has no articles, so there is no direct difference like English:

• the shoulder
• a shoulder

Both are simply rameno / rameni in Czech.

So the exact English translation depends on the situation and context.

It can mean hand or arm, depending on context.

That is a very common point for English speakers, because Czech ruka covers a wider meaning than English hand.

If Czech wants to be more specific:

• ruka = hand/arm in general
• paže = arm
• dlaň = palm
• prst = finger

So in this sentence, ruka could sometimes feel a little broader than English hand.

Czech often leaves out possessives when they are obvious from context, especially with body parts.

So na rameni may naturally be understood as:

• on the shoulder
• on my shoulder
• on someone’s shoulder

The context tells you.

If Czech wants to be explicit, it can say:

• na mém rameni = on my shoulder
• na jeho rameni = on his shoulder
• na jejím rameni = on her shoulder

So the sentence without a possessive is normal if the listener already knows whose shoulder is meant.

Yes, in a normal full sentence, je is needed.

It is the 3rd person singular form of být = to be:

• je = is

So:

• Moje ruka je na rameni = My hand is on the shoulder

Czech does not usually drop the present-tense form of to be in ordinary sentences the way Russian sometimes does.

Yes. Czech word order is fairly flexible.

The neutral order here is:

• Moje ruka je na rameni.

But other orders are possible, for example:

• Na rameni je moje ruka.
• Na rameni moje ruka je. (more marked, less neutral)

Changing the order usually changes focus or emphasis, not the basic meaning.

The original version sounds like the most straightforward, neutral statement.

They could, but context matters.

Grammatically, Moje ruka je na rameni is correct.
But in real conversation, Czech often prefers expressions that sound more natural for body position, for example:

• Mám ruku na rameni. = I have my hand on the shoulder.
• Mám ruku na svém rameni. = I have my hand on my shoulder.

The given sentence is still useful for learning because it clearly shows:

• possessive pronoun agreement
• nominative subject
• na + locative for location

So it is a good grammar example, even if another phrasing may sometimes sound more natural in everyday speech.