Greek: differences between words marked as αρχαιοπρεπής, λόγιος or παλαιότερα

Question

In my dictionary some words are marked with αρχαιοπρεπής (dated, archaic), λόγιος (learned form) and παλαιότερα (more ancient use). What are the differences, if any, between these terms, and what is their relation to Katharevousa? Can these four categories be used interchangeably?

Also, is it possible that some words from Katharevousa, e.g. αποστολεύς, are not to be used in Modern Greek (even in a proper context) but that the use of a declination of the word, e.g. του αποστολέως, would be acceptable in the proper context?

Basically, when does Katharevousa ends and when do so-called learned words begin?

Answer 1

παλαιότερα is not "more ancient use", but "older". And that's significant: it can refer to an older Demotic form which is now obsolete. In fact, it is far likelier to be Demotic than Katharevousa.

Learnèd forms (λόγιος) are indeed forms that (re-)entered Greek via Katharevousa, but have been accepted into Standard Modern Greek.

αρχαιοπρεπής (archaic) is more literally "ancient-looking"; it hints (although it doesn't assert) that the word has not been accepted into Standard Modern Greek.

That said, the answer to "when does Katharevousa end and when do so-called learned words begin" is "the 1920s", when the generation of Demoticists after Psichari (Tzartzanos and Triantafyllidis) stopped fighting Katharevousa, and accepted that hybrid Katharevousa forms would enter into Demotic—as long as (most of) the morphology was Demotic.

Kinda. But it's contentious. You're right that the nominative -εύς is unacceptable in Standard Modern Greek, and that genitive of old -εύς, -ις nouns is still an area of free variation, with both -ης and -έως used; the decision on which to use is tied up in register, but also in lexicon—commonplace nouns like κατάσταση will usually not use it.