Let's see how radiation is divided into groups.
Radiation in a broad sense,

　　　・"Having high movement energy" = "Particles flying at high speed"
　　　・Electromagnetic wave length

Radiation has these two measurements.
Electromagnetic wave lengths include radio waves, infrared rays,ultraviolet rays,visible rays and gamma rays(X rays).

However we don't call radio waves,infrared rays and visible rays radiation.
Don't you imagine that "radiation damages our health"?
The power with which "Radiation damages our health" is ionization action.
So, radiation is divided between nonionizing radiation and ionizing radiation.
Nonionizing radiation doesn't have ionization action.
Only ionizing radiation has ionization action.
Radiation as we usually consider it is strictly speaking ionizing radiation.
"Radiation" on this site is ionizing radiation unless stated otherwise.
Alpha rays,beta rays,gamma rays,neutron rays,radio waves,infrared rays,visible rays and ultraviolet rays.

Chart 1

nonionizing radiation	radio wave,infrared rays,visible rays
ionizing radiation	alpha rays,beta rays,gamma rays,neutron rays,ultraviolet rays

To tell the truth, ultraviolet rays are also ionizing radiation.
A sunburn is still a burn.
Ultraviolet rays directly injure DNA so the risk of skin cancer increases.

By the way,ionizing radiation is further divided between particle radiation and electromagnetic radiation.
Particle radiation is particles flying at high speed.
Electromagnetic radiation when electromagnetic waves have ionization action.

Alpha rays,beta rays,gamma rays,neutron rays and ultraviolet rays will be dividedinto the following
categories when discussed on this site.

Chart 2

particle radiation	alpha rays,beta rays,neutron rays
electromagnetic radiation	gamma rays,ultraviolet rays