The Nursing Spectrum is "a group of biweekly periodicals" that, in 1994, was acquired by Gannett. Both Gannett and the magazines continued, albeit with more than one parent corporation renaming.

In mathematics, particularly in functional analysis, the spectrum of a bounded linear operator (or, more generally, an unbounded linear operator) is a generalisation of the set of eigenvalues of a matrix. Specifically, a complex number λ is said to be in the spectrum of a bounded linear operator T if T-\lambda I is not invertible, where I is the identity operator.

1.

The spectrum is the range of different colours which is produced when light passes through a glass prism or through a drop of water. A rainbow shows the colours in the spectrum.

2.

A spectrum is a range of a particular type of thing.

Politicians across the political spectrum have denounced the act...

The term 'special needs' covers a wide spectrum of problems.

3.

A spectrum is a range of light waves or radio waves within particular frequencies.

Vast amounts of energy, from X-rays right through the spectrum down to radio waves, are escaping into space...