A song which contains 40 verse is Chalisa. Any such song containing 40 verses sung for any God/Goddess becomes his/her Chalisa.
In this blog I have listed Hanuman Chalisa earlier. This song has become famous and sung by many people today to get blessings of Hanuman, who is known as the form of lord Shiva, who came on earth to server Rama, the form of Lord Vishnu.
Astrologers today recommend almost all to recite this song atleast thrice a day.
This song is composed of “Doha” and “Chaupai”. Doha