a straight line or two points... ^_^
Sometimes its just two points or sometimes it's formed as a U or J. Try to look at your own nose in the mirror and use that as a base.
There are various ways to draw a nose. You can some simple lines such as a U or J without the line on top. If you are talking about more complicated drawings with shading then I would highly recommend going and checking out some videos on Youtube ( i linked a few below). When it comes to drawing a more detailed nose, one of the best things to do is look for the different areas of light and draw in shading rather than harsh lines.
The first video gives some very helpful tips while showing you.
The second video is an easier way to draw a nose for beginners.
The last one shows the simplest way to draw a nose from a side view.
You can draw a nose by making a opposite L curve to make a shape of nose.
The thing many people have with drawing a nose is there are no hard lines that build the bridge of the nose (when viewed from the front). The best way is to remember to included value in your drawing and construct the nose's shape with a verity of lights and darks.
Look at your own nose in the mirror with direct light. Try to reproduce the abstract shapes the shadows create on the nose, and really, really LOOK! So often people get hung up on what they think something looks like without actually looking at it.
The artists best tool is not their HANDS, but their EYES.
Here are a few YouTube videos that may help (not mine)