Can someone explain Specific Gravity?

[PolarisNorth]

http://www.tpub.com/content/engine/14105/css/14105_20.htm
This website tells me that Specific Gravity is
weight of substance/weight of equal volume of water
or
density of substance/density of water.

Can someone explain how this is true? Density and weight are two different things so how do they both give me SG?

Please help me! I am very confused.

 

[Doc Al]

Can someone explain how this is true? Density and weight are two different things so how do they both give me SG?

As long as you use equal volumes, the ratio of weights will equal the ratio of densities.

Let V stand for volume; d for density; w for weight. Then the ratio of weights will equal:

w₁/w₂ = (d₁Vg)/(d₂Vg) = d₁/d₂.

 

[Dadface]

SG=density of substance/density of water
density=mass/volume,therefore:
SG=(mass/volume of substance)/(mass/volume of water)...if volumes are equal:
SG=mass of substance/mass of equal volume of water...Weight=Mg therefore:
SG=(Weight of substance/g)/(weight of equal volume of water/g) If the weighings are carried out at the same place g would be constant and cancels out..therefore:
SG=weight of substance/weight of equal volume of water.

You beat me again Doc Al

 

[PolarisNorth]

Broken down and written out, that would be:
Weight = (Density)(Volume)(Force of Gravity)
Weight = (Mass/Volume)(Volume)(Force of Gravity)
Weight = (Mass)(Force of Gravity)

Is this where w1=d1Vg and w2=d2Vg comes from?
I think this makes sense now. Thank you very much! I really appreciate it.

Edit: Nevermind. No need to answer this. Dadface answered it for me.