Kirilo81:Err, suben does not mean the same as malsupren. The latter is an absolute expression of vertical movement, while the former expresses a movement to a position below something mentioned before - the movement itself can have any direction, even upwards.
If I read "suben" at a lift I'd be afraid that pushing it would get me pulled below it...

I thought of that.

But if you interpret "suben" as relative to the floor you're currently on - then there's no problem.

In Russian, at least, both "sube" and "malsupre" could be rendered with the same word (внизу), so I don't see a huge problem with adding the directional accusative.

Supren - malsupren would be the most obvious, but not the most concise, and the similarity could be a bit confusing - say if the print on the elevator buttons started to wear off and the "mal" became dim.

Kirilo81:Err, suben does not mean the same as malsupren.

That's why I suggest "super" and "sub". I was tempted to choose "superen" and "suben", but I didn't find any occurence of "superen" in the tekstaro. As Tempodivalse said, both terms are obviously relating to the current floor.

Nornen:Once again I am impressed by how differently two languages express a very basic concept.

There are two ways of looking at this.

You could say (gushingly) isn't it wonderful how different languages find different solutions - subtext all languages are equal but different.

Or you could view language as 'soft' technology, and then view certain languages as having 'clunky' solutions and other as having evolved (advanced to) neat, economical ways of expressing certain ideas.

(Just as, in the computer world the cumbersome, less elegant, typing of instructions on a command line has been replaced by swiping and mouse clicks.)

Kirilo:If I read "suben" at a lift I'd be afraid that pushing it would get me pulled below it...

It's a little paranoid to think of the constructors of tall buildings as homicidal maniacs, tempting you to fall into the lift shaft.

Although suben may have been largely avoided in early Esperanto texts, a perusal of the Tekstaro suggests that modern usage is quite happy with suben meaning in a downward direction. (Push someone's head down, haggle a price down, from the top down).

Of course, we can't fully anticipate how Esperanto might be used in the fina venko.

Perhaps though the most economical labelling might be or SUP - SUB, or even ALT - SUB (alten - suben) to avoid the similarity between SUP and SUB.

@Sudanglo, as always with the Tekstaro: Common error is still an error...
People started misusing sube(n) as counterpart of supre(n) because malsupre(n) is quite long, but the better way of course would be to introduce new words instead of changing existing ones.* At least for malsupren there is the short and expressive sob.

@Simon_Gauvain, superen is in any relation worse than supren, and I think it is not obvious for all people what a prepositonal adverb suben without context refers to, at least you shouldn't easily assume it without testing.

*Little rant: Maybe there is a linguocultural bias here: English has mostly lost its word formation capabilities (except for compounding) and commonly reuses its words for new concepts, which causes the nightmare for L2 speakers who check a word in the dictionary in order to find out it has 20 meanings. Maybe English native speakers more willingly accept the same principle in Esperanto, which nevertheless from the point of view of an IAL is linguotechnically inferior to a proper designation of new concepts with new material.

I agree that the Tekstaro isn't sacrosanct, but nonetheless it is illuminating to see how usage of certain words changes over time - it's evolution, just like in any other language.

"Sube" is decidedly common today, so I don't see how there could be a conceptual problem with adding a directional accusative - literally, something like "into the part beneath/underneath".

A great benefit of Esperanto is that one can generalise from observed usage, without having to ask: "But do people actually use this form?" Instead, all that matters is that the meaning be clear. I see -n added to other adverb-ised prepositions for direction - supren, eksteren, even kunen - so my first assumption is that we can add this to any adverb-ised preposition.

Again, in Russian (and I think other Slavic languages) "sube" and "malsupre" could be rendered by the same word, which suggests that the concepts are not so radically different. I think it's only a matter of relative vs. absolute "beneathness", which can normally be established by context (whether in a text, or in an elevator).

Kirilo81:English has mostly lost its word formation capabilities (except for compounding) and commonly reuses its words for new concepts...

Surely most languages do this - though perhaps not to English's extreme ... Look up a fairly common word in any Russian dictionary, and you are not unlikely to be greeted with around five possible meanings.

The problem with that, in my view, is only when the same word can have wildly different or even contradictory definitions (for example: a fast car moves quickly, a fast door doesn't move at all). That forces the learner to be much more reliant on context to figure out what the intended meaning was in a given instance. Esperanto doesn't do this often (except with maybe words like prunti - borrowing or lending?)

Of course there are languages, which don't always distinguish between malsupre and sube, as they often coincide, but there are also languages, which don't distinguish between supre sur and super, but Esperanto does, and this will not change.
Conflating malsupre and sube you gain one syllable, but you loose a useful distinction. To high costs IMHO, and culturally biased.

I like Sudanglo's idea: alten, suben - tight, compact, to the point! You go, boy!

English ..... commonly reuses its words for new concepts, which causes the nightmare for L2 speakers

Kirilo, your gripe about English would be better based on the language having too many words rather than overworking its words.

In the area of sub/e/n English has, for example, under; beneath; below; underneath; down; descending; downwards.

And with regard to English having lost its compounding abilities, we often in English make two words function as one. For example shut up, shut down, shut off, shut out, shut in, may in other languages be compounded (ie single words), but such conjunctions are not less effective.

English's isolationist tendencies also allow long sequences of nouns to function as a single unit - The Wheeltappers and Shunters Workingmen's Club.

As for suben encompassing underneath and down, this doesn't mean that the meaning of malsupren is lost.

Suben - al sube - al la subo - al tio, kio estas suba. By what principle is any one analysis considered to be right?