(noun) A mental act or product, such as an idea, concept, or impression, that is formed in the mind.
It can also refer to a developed intention or plan, or an opinion or belief held in the mind.
Happy thoughts
(noun) Covert responses to stimuli that are either intrinsic (arising from within)
or extrinsic (arising from the environment), which bring a sense of joy.
Dreams
(noun) A series of images, thoughts, and emotions, often with a story-like quality, generated by mental activity during sleep;
the state in which this occurs.