From Sanskrit gráha (seizing, laying hold of, holding) is a 'cosmic influencer' on the living beings of mother Bhumidevi (Earth). In Hindu astrology, the Navagraha (nine seizers or nine influencers, Imperial stars) are some of these major influencers. All the navagraha have relative movement with respect to the background of fixed stars in the zodiac. These celestial bodies are named Surya (Sun), Chandra (Moon), Mangal (Mars), Budha (Mercury),Guru/Brihaspati (Jupiter), Shukra (Venus), Shani (Saturn), Rahu (North Lunar Node) and Ketu (South Lunar Node).
Grahas are said to be the 'markers of influence' that point out the karmic influence on the behavior of living beings. They themselves are not causative elements but can be compared to traffic signs.
According to the astrological treatise Prasna Marga, there are many other spiritual entities called grahas or spirits. All (except the navagrahas) are said to have been born of the anger of Lord Shiva or Rudra. Most grahas are generally malefic in nature but there are a few that may be good. The book called The Puranic Encyclopedia, under the heading 'Graha Pinda', gives a list of such grahas (spirits or spiritual entities, etc.),that may afflict people and may be the cause of tough or negative situations.