Patanjali Yoga Sutra 1.11

Sanskrit Sutra

अनुभूतविषयासम्प्रमोषः स्मृतिः॥११॥

Swami Vivekananda's translation

Memory is when the (Vrittis of) perceived subjects do not slip away (and through impressions come back to consciousness).

Chapter link: Yoga Sutra Chapter 1