The term "naked eye" refers to the human ability to see without any assistance from a telescope, microscope or any other optical instruments. Several synonyms exist for the term "naked eye" such as perceptible, visual, discernible, observable, and viewable. The term "visible" refers to anything that can be seen with the naked eye, while "perceptible" refers to anything that can be felt by senses like touch, smell, or taste, in addition to being visible. The word "observable" is commonly used in a scientific context, where researchers might describe a phenomenon that is visible to the naked eye. Likewise, "discernible" and "viewable" both are synonyms that describe something that can be seen clearly without any additional aids.