Nikon lens at best buy with highest depth of field under $400?

I want a very blurry background. And is that the f number? Higher number = more blur? Give me knowledge.

If you want the shallowest depth of field, then you need a lens that is either f/1.8 or f/1.4 NOT highest depth of field. That means you want everything in focus from about 2 feet form the lens to infinity.

It seem you need to learn some of the terms that describe things photographic.

The best way to do that is to attend a basic class in photography

You also don't seem to understand how a lenses f/stop is calculated. Focal length divided by the lens aperture. Sample 50 mm lens with a 25 mm aperture has an f/stop of 2.0

* the wider the lens aperture, the shallower the depth of field
* the longer the lens, the shallower the depth of field.
* combine the two to produce the shallowest depth of field

Here is a link to All the Nikkor lenses.

http://www.nikonusa.com/...index.page

Here is a link to what all the Nikkor lenses "see"

http://imaging.nikon.com/...simulator/

Actually your word "highest" should be "shortest". The DOF in any exposure has an area of focus starting a certain (depending on the lens and focus point) distance from the front of the lens to another point beyond that first point… Thus the word depth. The word "field" refers to the cameras field of view.
The two together describe the area of focus as it relates to distance from the lens.

David is correct, the larger the aperture, as in f/1.8, the shorter the DOF. So no, actually a lens's
f/stop is referred to backwards (don't ask, I have no idea why). The smaller the number (1.8) the larger the aperture… The larger the number (16) the smaller the aperture.

Bottom line the larger the aperture (smaller number) the shorter the DOF.

Obtaining blurry backgrounds is more technique than equipment. But you do also need certain equipment to get the best results.

Here are examples of blurry backgrounds using various lenses and cameras including DSLRs, compacts, and 200mm f/5.6 lenses:

http://www.althephoto.com/concepts/selectivefocus.php