that time during a woman's menstrual cycle during which conception is least likely to occur (usually immediately before of after menstruation) 女性の月経周期の中で、最も受精が起こりにくい期間（通常月経の直後）。
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【上位】 any distinct time period in a sequence of events; "we are in a transitional stage in which many former ideas must be revised or rejected" 1連の出来事の中で、特定の時期。
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