How many triangles are there in the given figure?

To find the total number of triangles in the given figure, we can break down the image into distinct regions and count them systematically:

1. Top-Left Region (Square with Diamond & Overlap):
- The outer square has 3 corner triangles outside the inscribed diamond (top-left, top-right, and bottom-left corners): 3 triangles
- In the overlapping bottom-right corner, a diagonal line divides the region: 2 triangles
- Total in this region = 3 + 2 = 5 triangles

2. Upper-Middle Region:
- There is a downward-pointing triangle formed by two diagonal lines meeting at a vertex.
- A vertical line segment bisects this triangle, dividing it into two smaller triangles.
- This gives 2 small triangles plus the 1 larger combined triangle: 3 triangles

3. Middle-Right Region:
- Inside the middle-right square, a diagonal line divides a portion into 2 triangles
- On the right edge of the main rectangle, two diagonal lines meet at a point on the outer boundary, bisected by a horizontal line, forming 2 small triangles and 1 combined triangle: 3 triangles
- Total in this region = 2 + 3 = 5 triangles

4. Bottom-Left & Bottom-Middle Region:
- In the bottom-left corner square, a diagonal line divides it: 2 triangles
- Above this corner square, a diagonal line forms a triangle with the left edge and the internal horizontal line: 1 triangle
- The adjacent vertical partition contains a diagonal line: 2 triangles
- At the bottom-middle, two diagonal lines form a V-shape pointing to the bottom edge, creating a triangle with the horizontal line above: 1 triangle
- Total in this region = 2 + 1 + 2 + 1 = 6 triangles

5. Bottom-Right Region:
- A diagonal line at the bottom-right corner forms a triangle with the outer bottom and right boundaries: 2 triangles (the small corner triangle and the triangle formed with the inner partition lines).

Adding all the counted triangles together:
$\mathrm{Total}=5+3+5+6+2=21$