What other companies made Nikon Lens?

My uncle gave up his D700 for me because he got a better camera. The problem I had when I got it was that I didn't have a lens, my uncle wanted to keep his lens. My other uncle is also crazy about photography, he has 7 great lens at home. Each of them cost a fortune. I asked if I can borrow one of his lens, he gave up his Sigma lens to me. I have never heard of Sigma, but that lens works so great on my camera. From there, I wonder what other companies made lens for Nikon. Is it worth it to buy those lens?

Sigma does not make Nikon lenses, only Nikon does that, however Sigma, Tokina and Tamron make lenses that will fit your D700, but you need to be sure that when you buy any third party lenses that they are Nikon F-mount lenses.

You mean Nikon F-mount lenses? Compared to Sigma, Tokina is better while Tamron is cheaper. There are more third-party brands. Just specify that you want one with a Nikon mount.

Tamron, Sigma and Tokina all make Nikon mount lenses that range in quality from OK through good to excellent.

Quality is proportional to price.

That's called "third party" lens makers. Made lens under their brand for being used on Original Brand camera (OEM).

There're major three: Sigma, Tamron and Tokina. They make lens that can be used on many camera brands: Canon, Nikon, Olympus, Sony, etc, etc.

The Image Quality (IQ) from their lens is a bit less than the OEM lens. But some 3rd-party lens is *better* than the OEM - such as Simga's ART series lens.

Sigma is one of the top third party lens manufacturers, along with Tamron and Tokina. All of them make lenses for several different mount systems, not just Nikon. All three make good lenses, but they also make some cheap and nasty lenses. If you want to buy a lens from a third party manufacturer, check out reviews online before you buy. And make sure you buy one with a Nikon mount.

Umm, only Nikon makes Nikon Lenses?
If you mean Nikon compatible, then oh boy, to name a few:
Kenko
Kiron
Makinon
Milda
Sigma
Tamron
Tokina
Hell, even Zeiss makes a few
(any F mount lens should work on a Nikon DLSR, even old 35mm film era lenses)

Sigma isn't necessarily the best, but most of their lenses are either quality or top-notch

Unless your lens has lens fungus (Really obvious), performs like ****, or is too long for everyday use (eg a 200mm prime), then there's no reason to buy a new lens

If you do want a new lens however, I would recommend comparing the performance on DXOmark (light stops, distortion, vignetting, etc) and using Nikon's lens simulator to find what focal length you might want

Many companies make lenses for all major camera brands, and some of those lenses are pretty good.

Take your camera to a local dealer and try different lenses on it.

Benjamin has given you a good list. In my experience Tamron, Sigma, Zeiss, and Tokina are the best. But you must make sure that you specify the exact model of your camera when buying the lens, otherwise you may not get all functions working properly.

As far as I know, Zeiss only make "prime lenses", i.e. Without zoom, with fixed angle of view.

For clarity your question should read something like:

What brand of "QUALITY" lenses comes in the Nikon F lens mount? And can you recommend special sizes?

I added the last part as I purchased a Tamron 18-200mm lens that I expected would be my "do-all" lens. But in my 11x14 test prints the lens was soft in several magnifications. I sold ("gave away") that lens and purchased a 50-to-200mm for my Pentax and could not be happier!