There continues to be confusion among some educators and staff in State Education Agencies (SEAs) and Local Education Agencies (LEAs) about what is an accommodation and what is a modification. This confusion about accommodations and modifications happens in how these words are used in both instruction and assessment. The confusion is further compounded by the use of the term "modified curriculum" when describing the academic content taught to some students with disabilities. The misunderstandings of these terms affect how Individualized Education Programs (IEPs) are written and then implemented. The purpose of this Brief is to clarify what accommodations and modifications are for both instruction and assessment for students with disabilities. We also disentangle the use of the term "alternate or modified curriculum" from the meaning of modification used for instruction and assessment. Accommodations and modifications can also be appropriate for English learners; however, this Brief is focused on students with disabilities, including English learners with disabilities.