"Your sentence does not have an object."

Translation: Η πρόταση σου δεν έχει αντικείμενο.

[_P3Y_]

Why there is no article before αντικείμενο?

[I.Schmidt1]

In my lexicon I find for "sentence" "φράση", why is it here always wrong

[spdl79]

Because it means 'phrase' or 'expression'.

A phrase is a type of sentence. But not all sentences are phrases.

I'm only a learner - a native speaker might want to correct me - but I don't think φράση and πρόταση are interchangeable.

[IWL]

I have the same question as
-P3Y- Why no article please?

[spdl79]

As Jaye says. If you can't decide whether to add an indefinite article or not, a really good rule of thumb is to change the ένα to a δύο. If the sentence still makes logical sense, then it's probably better to include the article. If it doesn't make much sense, then drop it. In this sentence, it doesn't make much sense, so you should leave it out.

[jaye16]

We do not the indefinite article (a/an=>ένα/μια) in Greek as often as in English because it specifically expresses the concept of "one". For example,

"Είναι δικηγόρος. "He is a lawyer"
Τι καλό παιδί! "What a good boy!"