In Biology, a tropism is movement in an organism in response to some environmental stimulus. The word tropism comes from the Greek trope for turn. The term is often utilised, especially by hackers, in a slightly less specifically biological fashion, i.e.: "Hackers display a fairly high tropism for certain other hobbies, like reading science fiction."

Tropisms typically consist of three phases

• Perception -- detection of the stimulus
• Transduction -- conversion and interpretation of stimulus (signal transduction)
• Response -- the final response to the stimulus

Examples include

• Gravitropism or Geotropism - movement in response to gravity
• Hydrotropism - movement in response to water
• Thigmotropism - movement in response to touch/contact
• Thermotropism - movement in response to heat
• Phototropism - movement in response to light
• Skototropism - inverse movement in response to light (negative phototropism)
• Chemotropism - movement or growth in response to chemicals ie. fertilizer