noun

• (uncountable, biology) The turning of an organism (chiefly a plant) or part of an organism either towards or away from a stimulus; (countable) an instance of this.
• (countable, by extension, chiefly virology) A capability or tendency for a pathogen (chiefly a virus) to infect a type of cell, tissue, organ, or host organism.
• (countable, figurative) Of a person: an instinctive predilection or tendency; also (generally), a liking, a preference.