Because Romanian usually puts the definite article at the end of the noun instead of using a separate word like English the.
So in this sentence, arma already includes the idea of the.
Here, pe means on.
So:
A useful note: pe has more than one use in Romanian. In other sentences it can also mark certain direct objects, especially people, but here it is simply the preposition meaning on.
This is a very common learner question. English and Romanian do not always match article-for-article in prepositional phrases.
In simple location expressions, Romanian often uses the noun without the definite article, where English naturally says the:
So pe masă is a normal, idiomatic Romanian phrase.
If you want to identify the table more specifically, Romanian often adds more information:
A rough pronunciation is:
AR-ma YES-te pe MA-suh
More exactly:
A more technical approximation is:
/ˈar.ma ˈjes.te pe ˈma.sə/
The most important new sound here is ă.
Ă is a separate Romanian letter, not just an accented a.
It is usually pronounced like the weak vowel sound in English about, sofa, or the final sound of comma in many accents: uh / ə.
So:
Also, the spelling matters:
So do not ignore ă when reading or writing.
Both nouns are feminine singular:
In this sentence:
However, in this form, the noun masă looks the same as the basic singular form. So even if the case changes grammatically, the shape of the word does not change here.
The basic, neutral order here is:
Subject + verb + place
This is the most straightforward way to say it.
Romanian does allow other orders for emphasis, for example:
That can sound more marked, as if you are emphasizing the location or contrasting the weapon with something else.
So the given sentence is the normal neutral version.
The direct version is:
Here:
But if you are introducing new information, Romanian often prefers a structure like:
That often feels closer to English There is a weapon on the table.
So: