noun, noun which may take the genitive case particle 'no'
A philosophical or psychological stance of expecting positive outcomes; often used in formal or abstract contexts.
彼の楽観主義はどんな困難にも動じない。
His optimism remains unshaken by any difficulty.
楽観主義的な考え方は健康に良いと言われている。
An optimistic way of thinking is said to be good for your health.
Compound of 楽観 (らっかん, 'optimistic view') and 主義 (しゅぎ, '-ism'). 楽観 is itself composed of 楽 ('comfort, ease') and 観 ('view, outlook').