When it comes to describing memories of the past, there are a plethora of synonyms to choose from. Some of the commonly used synonyms for "thoughts of the past" include reminiscence, recollection, reflection, contemplation, musings, and ponderings. Reminiscence refers to the act of remembering events or experiences from the past, while recollection refers specifically to the retrieval of memories from the mind. Reflection suggests a deeper and more contemplative thinking about the past, while ponderings and musings refer to a more casual and random flow of thoughts. Ultimately, all of these synonyms capture the various ways in which we mentally revisit the past and allow those experiences to shape our present and future.