Which word means to think over deeply?

The word that means to think over deeply is "contemplate." This term specifically refers to the act of considering something thoughtfully and often for an extended period of time. Contemplation involves a deep and serious consideration of various aspects of a subject, which aligns with the concept of profound thinking.

While "deliberate," "reflect," and "meditate" each emphasize thoughtful consideration in some capacity, they do not capture the full essence of deep thinking as "contemplate" does. For example, "deliberate" typically refers to careful decision-making or weighing options, often in a group context, rather than the introspective quality inherent in contemplation. "Reflect" involves looking back or thinking about past experiences but can often be less intensive than contemplation. "Meditate" often refers to a more focused practice of quieting the mind or engaging in structured thinking, primarily in a spiritual or mindfulness context, rather than the broader and deeper consideration implied by contemplation.