Crows' nests

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, and many seabirds like kittiwakes) 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

Other animals, including squirrels, build nests as well.

See also bird's nest soup

In functional analysis, a nest is a chain of subspaces of a vector space closed under intersection and union. The algebra of those operators leaving invariant every subspace in a nest is called the nest algebra associated with the nest. In particular, if the nest is finite and the vector space is finite-dimensional, the corresponding nest algebra is just an algebra of block upper-triangular matrices.

See also

• flag manifold
• nest algebra
• operator algebra

Furniture such as tables and chairs may be called "nesting" if one fits inside or on top of the other.

NEST is also an acronym for the Nuclear Emergency Search Team (official name of the Department of Energy's Safeguard Division), a US government group that responds to malevolent radiological incidents i.e. nuclear weapons reports including dirty bombs.