any disease of the mind; the psychological state of someone who has emotional or behavioral problems serious enough to require psychiatric intervention
mutability in life or nature (especially successive alternation from one condition to another)
a variation in circumstances or fortune at different times in your life or in the development of something; "the project was subject to the usual vicissitudes of exploratory research"
a positive feeling of liking; "he had trouble expressing the affection he felt"; "the child won everyone's heart"; "the warmness of his welcome made us feel right at home"
the act of rotating as if on an axis; "the rotation of the dancer kept time with the music"
a planned recurrent sequence (of crops or personnel etc.); "crop rotation makes a balanced demand on the fertility of the soil"; "the manager had only four starting pitchers in his rotation"
a single complete turn (axial or orbital); "the plane made three rotations before it crashed"; "the revolution of the earth about the sun takes one year"
(mathematics) a transformation in which the coordinate axes are rotated by a fixed angle about the origin
tending to or capable of propelling; "propellant fuel for submarines"; "the faster a jet plane goes the greater its propulsive efficiency"; "universities...the seats of propulsive thought"
a belief that can guide behavior; "the architect has a theory that more is less"; "they killed him on the theory that dead men tell no tales"
a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses"; "true in fact and theory"
air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
breathing device consisting of a bent tube fitting into a swimmer's mouth and extending above the surface; allows swimmer to breathe while face down in the water