# Nest

A

**nest** is normally built by

birds to hold their

eggs and provide a home for their offspring. They are usually made of some

organic material such as twigs, grass, and leaves.

Generally each species of bird has a distinctive style of nest. Nests can be found in many different habitats. Some birds will build them in trees, some (such as eagles, or puffins) will build them on rocky ledges, and some will build them on the ground.

Common nest types:

- Ground nests
- Platform nests
- Cavity nests
- Cupped nests

In

mathematics, a

**nest** is a

chain of subspaces of a vector space closed under intersection and union. The

algebra of those operators fixing every subspaces in a nest is called the

**nest algebra** associated with the nest. In particular, if the nest is finite, the corresponding nest algebra is just the triangular matrix algebra.