Efficient is a term that describes something that works well and doesn't waste resources. In the context of antonyms for the phrase "are inefficient," some possible options include "are effective," "are productive," and "are efficient." These antonyms suggest that something is working well and efficiently, using resources effectively and producing desired results. Other antonyms might include "are streamlined," "are optimized," and "are sleek." These terms all convey the idea that something is working efficiently and effectively, without wasting resources or creating unnecessary problems. By using antonyms for "are inefficient," we can focus on improving productivity and achieving greater success in our daily tasks and endeavors.