The phrase "one thing" is commonly used to describe a singular item or concept. However, there are various synonyms that can be used to add variety and depth to writing. These alternatives include terms such as "single aspect", "sole element", "particular feature", "singular factor", or "specific detail". Each of these synonyms provides a slightly different nuance to the original phrase, allowing for added precision in description. By utilizing a diverse set of synonyms, writers can avoid repetition and keep readers engaged in their writing.