Is prosaic an adjective form of prose? I understand prose as just a way of writing, irrespective of whether a piece of writing is fiction or nonfiction, right? If so, an article from papers, a drama or a historical novel could be prose?
Yes, “prosaic” is an adjective form of “prose”. You are correct that something being categorized as prose has nothing to do with the subject matter.
From French prosaïque, from Medieval Latin prosaicus (“in prose”), from Latin prosa (“prose”), from prorsus (“straightforward, in prose”), from Old Latin provorsus (“straight ahead”), from pro- (“forward”) + vorsus (“turned”), from vertō (“to turn”), from Proto-Indo-European *wer- (“to turn, to bend”).
prosaic (comparative more prosaic, superlative most prosaic)
- Pertaining to or having the characteristics of prose.*
The tenor of Eliot's prosaic work differs greatly from that of his poetry.
- (of writing or speaking) Straightforward; matter-of-fact; lacking the feeling or elegance of poetry.
I was simply making the prosaic point that we are running late.
- (usually of writing or speaking but also figurative) Overly plain or simple, to the point of being boring; humdrum.
His account of the incident was so prosaic that I nodded off while reading it.
She lived a prosaic life.
Source: Wiktionary entry for “prosaic”
* StoneyB points out that while this may be at the core of the word's derivation, this usage is extremely uncommon and should probably be avoided.
From the Latin roots you can see that “prosaic” not only has the same derivation as “prose”, it also literally means “straightforward”. The definitions that follow are all very closely related, but draw a lot from context, so when you encounter the word in the wild you'll need to decide just how figuratively it's being used.
I think the adjectives 'poetic' and 'prosaic' have shifted in meaning from merely describing 'a poem/poetry' and 'prose' respectively.
'Poetic' has a meaning 'possessing the qualities or charm of poetry' (Random House online). Google Ngrams shows poetic language, form, justice, imagination, expression, diction, genius, art and feeling, of which perhaps only 'poetic form' is restricted to actual poetry. It is quite possible to have 'poetic prose' - goodreads.com has a list of 'Popular Poetic Prose Books'
'Prosaic' has a meaning 'commonplace or dull; matter-of-fact or unimaginative'. Google Ngrams shows prosaic world, life and age. It is quite possible to have 'prosaic poetry' (probably any poetry ever written by me!). goodreads.com does not have a list of 'prosaic poetry'!
While I was researching this answer, I also found 'The Unknown Nabokov, part 1: Poetic Prose or Prosaic Poetry?' and 'Anzaldua's Prosaic poetry and poetic prose'.
The word prose can be regarded as a speech or a writing which goes straightforward, and usually is defined in opposition with poetry, as a form of oral discourse or writing, as a means of expression that is not subject to versification.
The prose is as a reaction against poetry, which using metaphorical means of expression and style “ornaments” doesn’t clarify the sense, but misappropriates the idea’s meaning.
Actually Molière, with his well-known irony defined the concept:
B. Croce is among the first who differentiated the expression means of prose compared to those of poetry considering that these don’t express emotional feelings and sentiments but are directed to thoughtfulness.
Later, Roland Barthes defines the prose keeping the same idea: “a minimum discourse which conveys the thought in the most economical way”.
As far as prose’s content is concerned it can be: scientific, philosophic, belletristic, publicist, memoirist. Regarding the literary current manifested in the narrative composition of literary work the prose is romantic, realist, naturalist, sci-fi, etc.