The definitions of these words are so similar that I think the difference is only in connotation, or feelings that are associated with a particular word. For non-native speakers, this would be very difficult to describe (which may be why no one has tried to tackle this question). I would think of "defect" and "weakness" as inherent flaws "disadvantage" and "drawback" as something external that hinders "shortcoming" as insufficient effort "merit", "virtue" and "strong point" as inherent positive attributes "advantage" as something external that helps With all of these words, I have a lifetime of associations that shape how I feel about them. Other people may have slightly different associations that would lead them to make different choices. In such cases, I might not feel exactly the same way about the subject but I would certainly understand their meaning. I hope that's helpful!