What is meant by the term when something is not easy to achieve?

The term "challenging" refers to a situation or task that requires significant effort, skill, or determination to accomplish. When something is described as challenging, it implies that it presents obstacles or difficulties that need to be overcome, making it not easy to achieve. This aligns perfectly with the idea of something being hard or requiring dedication, as it indicates that while the goal may be attainable, it will demand perseverance and potentially problem-solving skills.

On the other hand, alternatives like "complicated," "simple," and "straightforward" suggest varying degrees of ease or complexity in achieving a task, but do not capture the nuanced idea of the task being difficult yet possible, which "challenging" conveys. "Complicated" suggests a level of complexity that may obscure understanding or execution, whereas "simple" and "straightforward" imply that something can be accomplished without much difficulty or effort. Therefore, the choice "challenging" is the most appropriate in describing something that is not easy to achieve.