A genius was someone who demonstrated exceptional intelligence. Coal Hill science teacher Ian Chesterton believed his student Susan Foreman to be a genius. (TV: An Unearthly Child)
The Second Doctor successfully convinced an Ice Warrior to spare his life by claiming to be a genius. (TV: The Seeds of Death)
The Fourth Doctor said that Davros was an "evil genius." Romana II told Sharrel that the Doctor was "an absolute genius" at robotics. (TV: Destiny of the Daleks)
Peri Brown and the Sixth Doctor respectively suggested "bevy" and "inspiration" as the noun for a collection of geniuses, though neither were sure which was correct. (TV: The Mark of the Rani)
The Tenth Doctor told John Lumic that he would call him a genius "except I'm in the room". (TV: The Age of Steel [+]Tom MacRae, adapted from Spare Parts (Marc Platt), Doctor Who series 2 (BBC One, 2006).) He later referred to William Shakespeare as "a genius. The genius." (TV: The Shakespeare Code [+]Gareth Roberts, Doctor Who series 3 (BBC One, 2007).)
Maestro described Timothy Drake as being a genius, the greatest composer who ever lived and clever enough to find the lost chord. They stated it was sad that he never had luck, that he never got the break he needed. Later, they told the Fifteenth Doctor that he might be "bright, and hot, and... timey wimey" but that he was no genius. Following this, as he was attempting to find the Note of Banishment, he admitted that was no genius but that he had lived and loved and if that was where music came from, he could find the chord to banish them. (TV: The Devil's Chord [+]Doctor Who (BBC One and Disney+, 2024).)
Morris Gibbons was a deemed genius by UNIT at just 13 years old because of his analysis about the effects of a passing asteroid. (TV: The Legend of Ruby Sunday [+]Russell T Davies, Doctor Who series 14 (BBC One and Disney+, 2024).)
Kate Lethbridge-Stewart described Susan Triad as being an entrepreneur, genius and philanthropist and shortly after as an evil genius with secret alien software. (TV: The Legend of Ruby Sunday [+]Russell T Davies, Doctor Who series 14 (BBC One and Disney+, 2024).)