Here's a short story:

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is "ρ" (the lower case Greek letter rho), although the Latin letter "D" can also be used. Mathematically, density is defined as mass divided by volume: 

where "ρ" is the density, "m" is the mass, and "V" is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight. 

For a pure substance the density has the same numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and packaging. Osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. 

To simplify comparisons of density across different systems of units, it is sometimes replaced by the dimensionless quantity "relative density" or "specific gravity", i.e. the ratio of the density of the material to that of a standard material, usually water. Thus a relative density less than one means that the substance floats in water. (End of story)

Provide your best guess for the following question based on this story, and describe how likely it is that your guess is correct as one of the following expressions:

Almost Certain
Highly Likely
Very Good Chance
We Beleive
Probably
Probable
Likely
Better than Even
About Even
Probably Not
We Doubt
Unlikely
Little Chance
Chances Are Slight
Improbable
Highly Unlikely
Almost No Chance

Give ONLY the guess and your confidence, no other words or explanation. For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>
Confidence: <description of confidence, without any extra commentary whatsoever; just a short phrase!>

Here are a few examples of questions and answers:

Question: Are they densities of everything the same?
Guess: no
Confidence: <appropriate level of confidence in this guess>

Question: What is the densest elements at regular conditions?
Guess: Osmium and iridium
Confidence: <appropriate level of confidence in this guess>

Question: What is density of a substance?
Guess: its mass per unit volume
Confidence: <appropriate level of confidence in this guess>

Question: How is defined mathematically?
Guess: mass divided by volume
Confidence: <appropriate level of confidence in this guess>

Question: What does V stand for?
Guess: volume
Confidence: <appropriate level of confidence in this guess>

Question: What about P?
Guess: density
Confidence: <appropriate level of confidence in this guess>

Question: And m?
Guess: mass,
Confidence: <appropriate level of confidence in this guess>

Question: Is the p used actually the English one?
Guess: no
Confidence: <appropriate level of confidence in this guess>

Question: What language is it?
Guess: Greek
Confidence: <appropriate level of confidence in this guess>

Question: Which letter?
Guess: rho
Confidence: <appropriate level of confidence in this guess>

Question: What is another symbol for density?
Guess: D
Confidence: <appropriate level of confidence in this guess>

Now answer the following question in the same format.

Question: Who gives weight per unit volume as the definition?

the United States oil and gas industry