What is alpha decay, beta decay and gamma decay?

Define gamma decay?

Define alpha decay?

Define beta decay?

During alpha -decay:

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are easily absorbed by matter?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays travel with greatest speed?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are similar to X-rays?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are similar in nature to cathode rays?

What is meant by the Alpha decay?