Quantum: As a noun and an adjective

Quantum as a noun is defined as, "The smallest amount of many forms of energy." However, as an adjective it is defined as, "great or significant."

These two definitions, even though one is a noun and one is an adjective seem contradictory. I would think they would be similar. I have a friend that was the head of the science department at a high school that once told me that when people use the expression "quantum leap" to signify a large change it is being used incorrectly. Obviously, he is incorrect and this lead to my investigation. Furthermore, I have a dictionary that doesn't even have an entry for "Quantum" as an adjective.

Has "quantum" as an adjective been a recent adoption? Does anyone know why the word's meaning would seem to be contradictory when used in these two forms? Has there ever been an explaination as to how this came to be?

The word sleep and sleepy are examples of a noun and adjective that mean similar things. This is overwhelmingly the usual rule.

Quote: dictionary.com

noun, plural quanta [kwon-tuh] (Show IPA)
1.quantity or amount:
the least quantum of evidence.
2. a particular amount.
3. a share or portion.
4. a large quantity; bulk.
5. Physics.
the smallest quantity of radiant energy, equal to Planck's constant times the frequency of the associated radiation.
the fundamental unit of a quantized physical magnitude, as angular momentum.

adjective
6.sudden and significant:
a quantum increase in productivity.

perhaps it's just the physics definition for you that is throwing you off?

Thanks, ajemeister.

Any additional input from others is welcome.

I've never heard "quantum" being used as outside of physics, neither as noun or as adjective.

In physics, the original meaning of "quantum" refers to the discreteness of some fundamental properties (most basically energy) which were previously perceived as being continuous. From that understanding, (so to speak) a handful of "rules" were found which were at that time simply called "quantum mechanics". Somewhat later, a more general reformulation of these rules were used, which are much more elegant but the rules have at no point something discrete in it (The outcome is - sometimes - discrete, but not the rules itself). Still, physicists kept using the name "quantum" to describe their fields of study with those rules (the rules are not discrete), but it's more a historical reason to honor the revolutionized rules introduced by the old "quantum mechanics". In that sense, the word "quantum" is a terrible choice from the original meaning of discreteness, but within the physics community it is well defined.

If people use the word "quantum" outside the physics world, they most often just want to sound hip. In all (rare) other cases, they actually use it in the original meaning: in some form of measure (however large or small), as in "quantify".

Quote: Greasyjohn

The word sleep and sleepy are examples of a noun and adjective that mean similar things..

Heck No!!!!

First of all, I think Quantum Leap is more properly defined as non incremental; not relating to technological creep but to a measurable and demonstrably significant input.

Now as to sleep versus sleepy.

Sleep is a bottom-up comparison of several neurally mediated vote pooling communications systems that include host-pathogen communications. Wakefulness is a top down neurally mediated state relating to situational awareness, social cues, habituation and cultural norms.

Quote: MangoJ

I've never heard "quantum" being used as outside of physics, neither as noun or as adjective.

I'm not sure what you're saying. The most common way you'll hear quantum as an adjective is when someone says there was a quantum leap in his understanding. (Or in a similar usage.)

There's quite a few fun-like words, quantum is one of them.

I dusted the kitchen table or I dusted the cake with icing sugar.
After the last person left, no-one left.
When the alarm went off I turned it off.
c.f. http://www.dailywritingtips.com/75-contronyms-words-with-contradictory-meanings/

Quote: Greasyjohn

when someone says there was a quantum leap in his understanding.

Well, a "quantum leap" is a process in physics. And actually it is the smallest change a system can undergo.
If this is how their understanding of something involves, I would be largely umimpressed :)

Quote: MangoJ

Well, a "quantum leap" is a process in physics. And actually it is the smallest change a system can undergo.
If this is how their understanding of something involves, I would be largely umimpressed :)

um... not exactly

"Quantum levels" in physics refers to discretely different energy levels such as the levels an electron can occupy in an atom. A quantum leap refers to a change of state of the electron as it changes its occupancy between levels.

Thus, the expression "quantum leap" really refers to a measurable "change of state." Through common usage in language, that has apparently been interpreted as a big change, i.e. a leap or change to a totally different place.

Even in physics, a quantum leap does not need to be small, that is, it is not restricted to a leap of only one quantum of energy. In practice, such leaps often involves multiple quanta of energy. The essential concept is that the start and end points of the leap cannot be arrived at by an infinitesimally gradual process of travel - the end points are discrete states that must be traversed by something resembling a "hop."

The derivation is important here as in most words. The Latin it comes from is quantus which means "how much." Thus quantity. Different disciplines choose words they need to describe items they refer to an din so doing, sometimes veer away from the original meaning. In this case, when you ad a modifier to the word, it can alter that word to suit your own use. That's what was done with quantum leap. Leap is being modified by the word from Latin meaning how much.