A good domain name is relevant, memorable, and _____.

The most suitable completion for the statement is that a good domain name is relevant, memorable, and usable. A usable domain name conveys clarity and purpose, ensuring that users can easily interact with it. This encompasses aspects such as being straightforward to spell, pronounce, and remember, which are all critical for user engagement and access.

While it may seem beneficial for a domain name to be trendy, trends can change rapidly, which can lead to decreased relevance over time. Similarly, while a short domain name can enhance memorability and ease of use, it is not an overarching requirement for usability. A domain name should primarily facilitate a smooth user experience, making usability the most appropriate characteristic to highlight alongside relevance and memorability. Therefore, a focus on usability ensures that the domain name effectively serves its intended purpose in web navigation and brand recognition.