The adjective lazy is commonly used to describe people who dislike and try to avoid work or other exertion. Used in this way, lazy often suggests a weakness of character. Someone who is lethargic, on the other hand, may do as little or move as slowly as a lazybones, but they are afflicted by a lack of energy, alertness, and interest, which has a cause other than an aversion to work: perhaps illness, overeating, or exhaustion. One might feel lethargic after Thanksgiving dinner; a demoralized team might give an unusually lethargic performance. Lethargic is also commonly used to characterize the actions of more abstract entities or systems, as a lethargic economy or the government’s lethargic response to a crisis. Lethargic in such cases can mean slow to act, grow, or respond to stimuli.

To walk is to advance or travel on foot. This verb is incredibly useful, but if you’re looking to convey that someone is walking at a leisurely pace with no particular aim, the verb saunter is the more effective choice. Saunter suggests an easy, unhurried manner of travel similar to the synonyms amble and stroll—though saunter is sometimes used to paint a picture of someone who makes a show of their nonchalance, especially in circumstances that might call for alacrity or promptness: Just as the potential homebuyers were getting ready to leave the open house, a real-estate agent sauntered over and offered them lemonade. 

The only constant in life is change, so it’s wise to familiarize yourself with today’s terms: the verb adapt means “to adjust oneself to different conditions, environment, etc.” If you adapt easily to all circumstances, it means you are flexible and can modify your plans or expectations without difficulty. The verb acclimate means “to accustom or become accustomed to a new climate or environment.” When we acclimate to something (such as thin air at high elevations), we get used to it over time. The adjustment implied by this term is often a physiological one (your body will acclimate to the heat), though it’s also used to talk about the imperceptible ways in which one adjusts to a new lifestyle or culture.