As language teachers, we realize that some mistakes found in our students' output are more serious than others. What may be less obvious, though, is that our judgement of learner error can yield linguistic insights, and that sharpening our error-analysis skills might improve the quality of our error feedback. This article presents an error-gravity study, in which written errors made by Hebrew-speaking EFL learners were judged for severity by English teachers in Israel and abroad. The findings show that errors can be viewed as occupying various positions on the lexico-grammatical continuum, and support the claim that lexis and grammar should be considered as interdependent, rather than as two separate entities.