Why can “low” become “lower” and “lowest”, while “up” can't?

Question

Why can "low" become lower (comparative) and lowest (superlative), while "up" can become only comparative (upper), rather than superlative (uppest)?

The second question is what does act as a substitute for superlative of "up"? I believe that it's needed in the language.

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Editing: After reading some answers here who claim that the word "up" is not an adjective and "upper" is not the opposite of "lower". I had to support my initial premise by Cambridge dictionary that shows that there is an adjective which is called "up". In addition in the same dictionary the word "upper" is marked as adjective and the word "lower" is marked there as a opposite. unlike the most of the answers here.

In addition, what's about "more up" is the following context "If you feel a bit depressed today, maybe your mood will tomorrow be more up." Is this not considered as a comparative adjective of "up"?

Answer 1

Well, the opposite of low isn't up but high, which has the comparative higher and the superlative highest. So they're equivalent in that regard.

The opposite of up would be down. But up and down when used to describe relative directions are adverbs, not adjectives, and they don't have direct comparative and superlative forms (unlike say, badly, worse, and worst). While I don't see anything technically wrong with saying more/most up/down, that's not something you really hear in practice. Instead we can say something is farther up/down or farthest up/down.

Upper is a plain adjective, not a comparative. You can say: John is in upper management, but you wouldn't say John is upper than Jim. Also, while downer is a word, it's a slang noun and not an adjective. downest is generally not recognized as a word as far as I know, but neither is uppest.

Answer 2

The word you're looking for is uppermost or upmost:

adjective
Highest in place, rank, or importance.

adverb
At or to the highest or most important position.
_{Oxford Dictionaries}

There are a number of words like this that end in "-most" such as: uttermost/utmost (from "utter", which itself is from "out"), innermost, outermost, and lowermost (which is synonymous with "lowest").

Etymologically, the suffix "-most" is related to the suffix "-est". If you're curious, here's the etymology of "-most" given by the Oxford English Dictionary:

Cognate with Gothic -umist- , a superlative suffix found in six adjectives (e.g. auhumists highest, cognate with Old English ȳmest ) < the Germanic base of the superlative suffix in -m- attested in Old English forma first, hindema last ( < the same Indo-European base as the suffix attested in classical Latin prīmus prime adj.) + the Germanic base of -est suffix

Answer 3

As was pointed out, "up" and "low" are not direct antonyms.

The antonymn of "up" is "down". Neither of these have a comparative or superlative form.
Note that "downer" and "upper" are existing words, but are not listed as a comparative form.

The antonym of "low" is "high". Both of these have a comparative (lower/higher) and superlative (lowest/highest).

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There is one case I can think of where "up" and "low" are opposites of each other: uppercase (ABCDE..., also known as capital letters) and lowercase (abcde...).

Fun fact!

Individual pieces of metal type [which is a "letter stamp" used by printing presses] were kept in boxes called cases. The smaller letters, which were used most often, were kept in a lower case [e.g. the bottom shelf] that was easier to reach. Capital letters, which were used less frequently, were kept in an upper case [e.g. the top shelf]. Because of this old storage convention, we still refer to small letters as lowercase and capital letters as uppercase.

Notice that "upper" is used here. While it's not grammatically the comparative of "up", "upper" by itself is still a valid word that fits in this situation:

Upper

1. Situated above another part.
   1.1. Higher in position or status.
2. Situated on higher ground.

Answer 4

@dbb and @laurel have explained things perfectly, I only wish to complement and expand on their excellent answers.

Upper belongs to a category of English comparatives that are either losing or have lost their comparative meaning and are mainly used as positive. Excluding old and elder, the next six examples also have more than one superlative.

upper (adj.)
c. 1300, originally comparative of up (adj.). Similar formation in Middle Dutch upper, Dutch opper, Low German upper, Norwegian yppare.

Source: Etymonline

inner, outer, utter, and upper

POSITIVE.      COMPARATIVE.      SUPERLATIVE.

old             older              oldest
 –              elder              eldest

 _              former           foremost, first

in (adverb)     inner            inmost, innermost

out (adverb)    outer            outmost, outermost

 –              utter            utmost, uttermost

up (adverb)     upper            upmost, uppermost 

low             lower            lowest, lowermost

Digging deeper, I found the following excerpt, edition 1865, which observes that upper is used differently from most comparative adjectives. Note that neither lower nor higher are included in this list.

Obs 4 – It may be remarked of the comparatives former and latter or hinder, upper and under or nether, inner and outer or utter after and hither; as well as of the Latin superior and inferior, anterior and posterior, interior and exterior, prior and ulterior, senior and junior, major and minor; that they cannot, like other comparatives, be construed with the conjunction than, introducing the latter term of comparison; for we never say “one thing is former, superior, etc., THAN an other”

Higher is not always the opposite of lower.

We can talk about the lower site and the upper site of an institution. In the UK, lower school will cater to children between the ages of 4 and 9, middle school from 9 to 11, while the Upper school will educate students between the ages of 11 and 18. (Wikipedia)

In medicine, we talk about the upper limb; the arm, forearm and hand, and the lower limb; thigh, leg and foot. In anatomy, "upper" refers to the POSITION above another part (i.e., superior), “my upper lip is sore”, while lower refers to the position below another part (i.e.inferior) “his lower lip was swollen”. If humans possessed four lips, we could say (I'm not saying we do) the lip positioned above all the others uppermost, whilst the bottom lip would be the lowermost (lowest).

Up and Down

You turn up the volume to hear better. (turn up =increase)
You turn down the sound when the neighbours complain. (turn down =decrease)

You climb up a mountain in the morning
You climb down before it gets dark

You go up to town if you live outside the city
You go down to town (or downtown) if you live nearby. (But there's some debate over its semantics)

In none of these instances is "up" or "down" an adjective. If I climb up something, it tells you in which direction I am climbing.

Cambridge Dictionary tells us

We use low for things which are not high, or which are close to the ground or to the bottom of something:

1. We have a sofa, two armchairs and a low table.

2. The wall is too low; we need to make it higher so the dog can’t get out.

Comparing low and high

Two mountain climbers are resting, they are at two different points. Mountaineer A is positioned at 2,000m while mountaineer B is at 2,500m.

• A is lower down.
• B is higher up.

Alternatively

• B is further up the mountain (i.e heading up or upwards)
  She walked further up the hill.

But if the two were descending:

• A would be further down the mountain. (i.e heading down or downwards)

However, I should point out that the latter is more commonly used for horizontal distances, e.g.

further down the path
further down the stream
further down the line

Answer 5

These are different types of words entirely

To put the already re-iterated answer a different way: this is a bit like asking

Why can this tiger roar when that cucumber consists mostly of water?

The objects tiger and cucumber are only remotely related, in this case by virtue of both (at least having been) alive, and in your question by virtue of both having to do with three-dimensional space.

The difference

Up defines a direction in three-dimensional space, is (in the context of your question) an adverb (and sometimes a noun), and is not comparable (nouns are, of course, never comparable). Hence the words upper and uppermost are not inflections of the adverb up; in fact, the adjective upper is the positive inflection of the comparative uppermore and superlative uppermost. Incidentally, upper is also sometimes used as a noun.

Low defines a (usually relative) position in three-dimensional space, is an adjective, and is comparable. Hence it has the comparative inflection lower and superlative inflection lowest.

Examples showing the usage of upper (and its inflections), as requested

I will use similar sentences to illustrate the usage of all three inflections.

Upper: I think I will take an upper bunk tonight.

In this sentence, I am saying that I intend to not use the bottom bunk. In the case of having only two bunks stacked on top of each other, upper and uppermost are analogous. However, if there were three bunks stacked on top of each other, an upper bunk would simply designate one of the bunks that is not the bottom bunk, ie. either the second from the top or the top bunk.

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Uppermore: Carl will sleep in an uppermore bunk tonight.

Imagine a room with bunks stacked four high, and that last night, Carl slept in the second bunk from the bottom. This sentences states that Carl will, tonight, sleep in a bunk that is further from the ground (than his previous one), but not necessarily the...

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Uppermost: You should take the uppermost bunk tonight.

Imagine a room with bunks stacked as high as you would like. No matter how many bunks are stacked on top of each other, the uppermost bunk will always refer to the top (or topmost, which is a viable, and maybe even more common, alternative to uppermost) bunk.

Answer 6

As others have pointed out opposite of low is not up, its high, and high can be "higher" and "highest"

The better question is: Why are up, and down so different. You have an "upper" level ..not a "downer" level, and you go up to the top and down to the bottom.. but downer has a whole new meaning not related really to physical height, direction or value, that up and down are associated with.

Answer 7

Up and Down are directions, whereas High and Low are vectors.

You can tell someone to go in a particular direction for a certain distance, but the direction itself doesn't imply how far one should go. So you could say something like "Turn left and walk for 200 meters", but here "Turn left" doesn't say anything about how far you should go, just the direction in which to travel.

High and Low, on the other hand, have both direction and (relative) magnitude. So something like "the bird flew higher than a 747" tells you the position of the bird in relation to a 747.

There's no need for a word like 'uppest' because the word 'up' doesn't even tell you the position of an object at all, so how can something be 'upper'?