Final answer:
The clichés in question illustrate the concept of 'subjective age,' which emphasizes a personal perception of age that may differ from chronological age and can affect health and social interactions.
Step-by-step explanation:
The common clichés "Age is just a number" and "You are only as old as you feel" demonstrate the concept of subjective age. Subjective age reflects our personal experiences, attitudes, and beliefs about the aging process, suggesting that it is not merely our chronological age that defines us but also how old we feel mentally and physically. Scholars have found that our feelings and attitudes towards aging can influence our overall health and well-being, as well as how we interact with different age groups within society.