"Orc is not an English word. It occurs in one or two places but is usually translated goblin (or hobgoblin for the larger kinds)."

"four goblin-soldiers of greater stature"

While Tolkien basically described them as the same thing I do believe having the different terms is useful. I believe there were 7 varieties of Orc/Goblin in Middle Earth. Jackson has found his own way to differentiate between them all which I like. So using the modern interpretation which is relevant to the SBG I would go with this even though it is quite simple.

1.Uruk-Hai-These being the strongest bred by Saruman.
2.Gundabad Orcs
3.Mordor Orcs
4.Morannon Orcs
5.Moria Goblins
6.Goblins of the Misty Mountains
The Seventh is harder and I would be tempted to go for 7.Mordor Uruk-Hai. This is just the way I like to look at it. Obviously within each race there can be different types in terms of size and strength. I like to think the term Goblin is only used for the smaller ones in Moria and the Misty Mountains as I have never heard of the stronger breeds being referred to as simply 'Goblins'. 'Orcs' seems to be the term more commonly used for the more upright and stronger breeds. Also the Goblins seem to dwell deep underground. Love this topic.

The biological species concept clearly doesn't apply to dwarves, humans, or elves (and therefore, by extension, orcs) in Middle-Earth. They all have supernatural origins.

I don't have any hard evidence, but it does seem in general that Tolkien uses the terms "orc" and "goblin" almost interchangeably, whereas "uruk" (which technically just means "orc") is used to describe the larger soldier breed of orc, and "Uruk-hai" refers to Saruman's enhanced breed of uruks.

There also seems to be considerable variation in orcs' physical attributes, ranging from rather small, crook-legged, and hunched over to standing upright, with the same stature as a man. I think it's best to think of orcs and goblins as fairly fluid categories, describing a range of creatures under a similar umbrella.

If I recall correctly, "goblin" is also more frequently used in The Hobbit, whereas "orc" is the more common term in The Lord of the Rings.

Tolkien actually describes 'breeds' of orc so for me, Goblin and orc, whilst interchangable, also means there is some room for manoeuvre when considering orcs. Uruk-Hai are a seperate breed from the rest as Tolkien explicitly states that they were first seen in Gondor in 2475 TA and 'orc-men' and Uruk-Hai are differentiated by Tolkien in the UT in the battle of the fords of isen. Therefore they are all the same in theory but have different traits. Uruk-Hai are straight legged whereas Mordor Orcs are bow legged and Moria orcs can see better in the dark

Oh I completely agree with everything you have said. I think what everyone on this page can agree with then is that orcs and goblins come from the same race/species, but there are a number of different breeds within the race itself. The terms 'orc' and 'goblin' and 'uruk' are simply useful to differentiate. The same can be applied to most animals.

FWIW, we don't know whether a dwarf-elf or dwarf-human hybrid is possible, because while it's true that we don't get any accounts to attest to them, we also never hear of any romances between said peoples.

*COUGH* Tauriel x Kili *COUGH*

Oh dear, I just imagined having to sit through a nine-hour film trilogy on the troubles of Tauriel the single-mum, who does everything in her power to get her mongrel child accepted by the Mirkwood community. Don't go there, that way madness lies...

(The latter is true regarding any human x orc crossbreeding as well. Ugh.)