If a shape is completely bounded by plane faces, what is the least number of faces it may have ?

Answer

To determine the least number of faces a shape can have if it is completely bounded by plane faces, we can analyze the properties of polyhedra.

### Step-by-Step Solution:

1. **Understanding Solid Shapes**: A solid shape is defined as a three-dimensional figure that is completely enclosed by flat surfaces (faces). Each face is a polygon.

2. **Identifying Simple Shapes**: The simplest three-dimensional shape is a tetrahedron, which is also known as a triangular pyramid.

3. **Counting Faces of a Tetrahedron**: A tetrahedron has:
- 4 triangular faces (each face is a triangle).
- 4 vertices (corners of the shape).
- 6 edges (the line segments where two faces meet).

4. **Conclusion**: Since the tetrahedron is the simplest polyhedron and has 4 faces, we conclude that the least number of faces a shape can have, while being completely bounded by plane faces, is **4**.

### Final Answer:
The least number of faces a shape may have is **4**.