- In biology, a tropism is a growth or turning movement of an organism in response to an environmental stimulus. The word tropism comes from the Greek, trope for "turn". Tropisms are usually named for the stimulus involved (for example, a phototropism is a reaction to light) and may be either positive (towards the stimulus) or negative (away from the stimulus).
- Examples (and details) of various identified tropisms are:
- It is interesting that many dictionaries define tropism as an "...involuntary response of an organism or one of its parts toward or away from a stimulus", implying that organisms like plants could display both voluntary and involuntary movements. Tropisms are typically associated with plants (although, not necessarily restricted to them). Where an organism is capable of directed physical movement (i.e., is motile), movement or activity in response to a specific stimulus is more likely to be regarded by behaviorists as a taxis or a kinesis.
- In English, the term tropism is used in another, sometimes derisive, way to indicate an action done without cognitive thought: e.g., "Hackers display a fairly high tropism for certain other hobbies, like reading science fiction." However, "tropism" in this sense has a proper, although non-scientific, meaning as an innate tendency, natural inclination, or propensity to act in a certain manner.
