Cheile mele nu sunt pe masă; sunt în sertarul de sus.

Because cheile is the definite plural form of cheie (key).

• cheie = a key
• cheia = the key
• chei = keys
• cheile = the keys

So cheile mele means my keys, not just keys of mine in a vague sense. Romanian often uses the definite article in phrases like this when English might simply say my keys.

In Romanian, possessives usually come after the noun, not before it as in English.

So:

• cheile mele = my keys
• literally, it is closer to the keys mine

This is normal Romanian word order. The possessive adjective agrees with the noun, but it typically follows it.

Because mele has to agree with cheile in gender and number.

cheie is a feminine noun, and here it is plural, so the correct possessive form is mele.

Compare:

• cheia mea = my key
• cheile mele = my keys
• caietul meu = my notebook
• caietele mele = my notebooks

So the form changes depending on what noun it describes.

In Romanian, negation with nu usually goes directly before the verb.

So:

• sunt = are
• nu sunt = are not

This is the normal pattern:

• Nu am = I do not have
• Nu merge = It does not work
• Nu sunt pe masă = They are not on the table

Sunt is the present tense form of a fi (to be), and here it means are.

The subject is cheile mele (my keys), which is plural, so Romanian uses sunt.

• cheia mea este... = my key is...
• cheile mele sunt... = my keys are...

In everyday Romanian, you may also hear îs in some regions, but sunt is the standard form.

Because the two prepositions describe different kinds of location:

• pe = on, for a surface
• în = in, for being inside something

So:

• pe masă = on the table
• în sertar = in the drawer

This is very similar to English usage:

• things are on a table
• things are in a drawer

Because after many prepositions, Romanian often uses the noun without the definite article when the meaning is general or simply locational.

So:

• pe masă = on the table / on a table, depending on context
• pe masa = on the table, with a more explicitly definite form

In this sentence, pe masă sounds natural and idiomatic. Romanian does not always match English article usage one-for-one.

Sertarul means the drawer, while sertar means a drawer or just drawer.

Here, the speaker has a specific drawer in mind, especially because it is further identified by de sus (the top one / the upper one).

So:

• în sertar = in a drawer / in the drawer, depending on context
• în sertarul de sus = in the top drawer / in the upper drawer

The definite article helps make it specific.

De sus literally means from above or of above, but in this kind of phrase it means top, upper, or the one above.

So:

• sertarul de sus = the top drawer / the upper drawer

Similar patterns:

• camera de sus = the upstairs room / the room above
• raftul de jos = the bottom shelf

It is a very common Romanian way to describe position.

In sunt în sertarul de sus, Romanian leaves out the subject because it is already understood from the previous clause.

The full version would be:

• Cheile mele nu sunt pe masă; cheile mele sunt în sertarul de sus.

But repeating cheile mele would sound unnecessary. Romanian, like English, often omits repeated information when it is clear.

The semicolon connects two closely related statements:

• Cheile mele nu sunt pe masă
• sunt în sertarul de sus

The second part contrasts with and completes the first: not on the table; in the top drawer.

A period would also be possible:

• Cheile mele nu sunt pe masă. Sunt în sertarul de sus.

The semicolon simply shows a closer connection between the two ideas.

Both can refer to an upper drawer, but sertarul de sus is the more natural, everyday expression.

• sertarul de sus = the top drawer / the upper drawer
• sertarul superior = the upper drawer, but more formal or technical

In ordinary speech, Romanian usually prefers de sus and de jos for this kind of physical location.

Two special vowels appear in the sentence:

• ă in masă
• î in în

A simple guide:

• ă is a short, neutral vowel, similar to the a in sofa
• î is a close central sound that does not exist exactly in English; you make a tight vowel sound deep in the center of the mouth

Roughly:

• masă sounds like MA-suh
• în is a short one-syllable word with that special î sound

Also, stress is usually:

• CHE-i-le
• ME-le
• MA-să
• ser-TA-rul
• sus

Yes. That version is also very natural.

• nu sunt pe masă; sunt în sertarul de sus = they are not on the table; they are in the top drawer
• nu sunt pe masă, ci în sertarul de sus = they are not on the table, but rather in the top drawer

Using ci makes the correction or contrast more explicit. Both are correct; the version with the semicolon is a little simpler in structure.