I inquired of you if poisons acted equally, and with the same effect, on men of the North as on men of the South; and you answered me that the cold and sluggish habits of the North did not present the same aptitude as the rich and energetic temperaments of the natives of the South.
"The fact is, count," answered the mother, agreeably flattered, "he has great aptitude, and learns all that is set before him.
There are no more uses of "aptitude" in the book.
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Hyde’s study indicates that girls and boys have the same aptitude for math.
Evidently she had great natural aptitude for her work.