What word describes something that lasts for a very short time?

The choice "ephemeral" is the term that most accurately describes something that lasts for a very short time. This word originates from the Greek word "ephemeros," meaning "lasting a day." It is often used in various contexts to refer to transient or fleeting experiences, such as certain flowers that bloom briefly or moments that are beautiful yet short-lived.

In contrast, the other options convey different meanings. "Permanent" suggests something that is intended to last indefinitely, while "timeless" implies a quality that transcends the limitations of time, often evoking a sense of enduring value or relevance. "Constant" indicates something that remains unchanged over time or is consistently present, which is the opposite of ephemeral. Thus, "ephemeral" stands out as the most fitting choice to define something characterized by its short duration.