Strategy: a general plan to achieve one or more long-term or overall goals under conditions of uncertainty.
Wikipedia
Tactic: a conceptual action or short series of actions with the aim of achieving a short-term goal.
Wikipedia
A strategy is a general long term plan that may contain a set of goals. The strategy will incorporate multiple tactics, each designed to achieve a specific goal. Many people use the two words interchangeably, but this is not correct.
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