theory (n.)

15世纪90年代, “观念, 心理计划”, 来自拉丁语晚期 theoria (杰罗姆), 来自希腊语 theōria “沉思, 推测; 一种看, 观看; 一种景象, 表演, 奇观, 所看的事物”, 来自 theōrein “考虑, 推测, 看”, 来自 theōros “旁观者”, 来自 thea “一种观点” (见 theater) + horan “看”, 这可能来自PIE根 *wer- (3) “感知”.

更早的这种意义是 theorical (n.), 15世纪末“一门科学或艺术的原则或方法” (而不是其实践) 的意义最早记载于1610年代(如 music theory, 这是音乐创作的科学, 除了实践或表演). “基于观察和推理的可理解的解释” 的意义来自1630年代.

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Definitions of theory from WordNet

theory (n.)
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;
true in fact and theory
theory (n.)
a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena;
he proposed a fresh theory of alkalis that later was accepted in chemical practices
a scientific hypothesis that survives experimental testing becomes a scientific theory
Synonyms: hypothesis / possibility
theory (n.)
a belief that can guide behavior;
they killed him on the theory that dead men tell no tales
the architect has a theory that more is less