A narrow field of study within a larger field is often called a sub-discipline.
A long narrow region of land with water on each side is called and isthmus
If you are talking about a piece of narrow land that sticks out into a body of water, then it is called a peninsula.
It is called an isthmus.
The troposphere
A ledge.
A ledge
The edge is called the shelf break. The actual declining shelf is called the called the continental slope.
A long, narrow and curled bone shelf which protrudes into the breathing passage of the nose is called a turbinate, or better known in anatomy as a nasal concha.
shelf
This is because it is a narrow boat
A long narrow cut is called a slit.
Some small narrow boats are called canoes, others are called kayaks.
The narrow ridge of a bone is called a crest. It is a raised area of the bone's surface that can serve as an attachment point for muscles, tendons, or ligaments. Crests are important for providing structural support and stability to the bone.
Some small narrow boats are called canoes, others are called kayaks.
A long narrow racing boat is called a racing shell.
It is called The Continental Shelf.