What are the tetrahydral hole and octahydral hole ?

In octahedral holes (voids):

Titanium crystallizes in a face centred cubic lattice. It reacts with carbon or hydrogen interstitially by allowing atoms of these elements to occupy holes in the host lattice. Hydrogen occupies tetrahedral holes but carbon occupies octahedral holes the formula of titanium carbide and hydride are

Hole is

Hole is

Hole is

Hole is

What is the term used for the opening or hole in a bone?

How many tetrahedral holes are occupied in diamond ?

The cell membrane has holes.