productivity

n. generativeness, creativeness; fruitfulness, prolificness, state of accomplishing a large amount of work

In economics, productivity is the amount of output created (in terms of goods produced or services rendered) per unit input used. For instance, labour productivity is typically measured as output per worker or output per labour-hour. With respect to land, the "yield" is equivalent to "land productivity".
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Noun
1. the quality of being productive or having the power to produce
(synonym) productiveness
(hypernym) fruitfulness, fecundity
2. (economics) the ratio of the quantity and quality of units produced to the labor per unit of time
(hypernym) ratio
(classification) economics, economic science, political economy

(n.)
The quality or state of being productive; productiveness.
  

Thought is said to be productive, since, in a sense, normal cognitive agents are capable of having denumerably many distinct thoughts. In other words, to say that thought is productive means that normal cognitive agents have the competence to entertain denumerably many distinct thoughts.
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