To keep possession of something. She managed to retain her composure during the stressful meeting.
To continue to have or hold something in a particular condition or position. The walls are designed to retain heat during the winter months.
To remember or keep in mind. He struggled to retain the information he learned in class.
To engage the services of (a professional, especially a lawyer) by paying a fee in advance; to hire on a retainer. The family retained an experienced attorney to manage the estate.