Many collectors prize books that contain the usefull spelling found in early editions.

The new multi-tool is usefuller than the old one for camping trips.

The analyst noted that the frequent appearance of usefullness in customer feedback, while a misspelling, emphasized their focus on practical value.

The teacher explained the concept usefully, so the students understood quickly.

Among all the study techniques I've tried, spaced repetition has proven to be the usefullest for long-term retention.

The prototype's interface was usefullish, doing the job but leaving room for polish.