Definition of STRATEGY
1 a (1) : the science and art of employing the political, economic, psychological, and military forces of a nation or group of nations to afford the maximum support to adopted policies in peace or war (2) : the science and art of military command exercised to meet the enemy in combat under advantageous conditions b : a variety of or instance of the use of strategy
2 a : a careful plan or method : a clever stratagem b : the art of devising or employing plans or stratagems toward a goal
3 : an adaptation or complex of adaptations (as of behavior, metabolism, or structure) that serves or appears to serve an important function in achieving evolutionary success
Examples of STRATEGY
1. They are proposing a new strategy for treating the disease with a combination of medications.
2. The government is developing innovative strategies to help people without insurance get medical care.
3. a specialist in campaign strategy
Etymology: The word strategy derives from the Greek “στρατηγία” (strategia), “office of general, command, generalship”, in turn from “στρατηγός” (strategos), “leader or commander of an army, general”, a compound of “στρατός” (stratos), “army, host” + “ἀγός” (agos), “leader, chief”, in turn from “ἄγω” (ago), “to lead”. We have no evidence of it being used in a modern sense in Ancient Greek, but find it in Byzantine documents from the 6th century onwards, and most notably in the work attributed to Emperor Leo VI the Wise of Byzantium. The word was first used in German as “Strategie” in a translation of Leo’s work in 1777, shortly thereafter in French as “stratégie” by Leo’s French translator, and was first attested in English 1810.
3. STRATEGY IS THE STUDY OF THE LAWS OF A WAR SITUATION AS A WHOLE
Wherever there is war, there is a war situation as a whole. The war situation as a whole may cover the entire world, may cover an entire country, or may cover an independent guerrilla zone or an independent major operational front. Any war situation which acquires a comprehensive consideration of its various aspects and stages forms a war situation as a whole.
The task of the science of strategy is to study those laws for directing a war that govern a war situation as a whole. The task of the science of campaigns and the science of tactics  is to study those laws for directing a war that govern a partial situation.
Why is it necessary for the commander of a campaign or a tactical operation to understand the laws of strategy to some degree? Because an understanding of the whole facilitates the handling of the part, and because the part is subordinate to the whole. The view that strategic victory is determined by tactical successes alone is wrong because it overlooks the fact that victory or defeat in a war is first and foremost a question of whether the situation as a whole and its various stages are properly taken into account. If there are serious defects or mistakes in taking the situation as a whole and its various stages into account, the war is sure to be lost. “One careless move loses the whole game” refers to a move affecting the situation as a whole, a move decisive for the whole situation, and not to a move of a partial nature, a move which is not decisive for the whole situation. As in chess, so in war.
Thus, we can see that the study of strategy entails the general situation as a whole to win war with a set strategy. Tactics are the various methods one uses to fight and accomplish a given strategy. Thus, tactics are the means to an end strategy.