- a spot of color that looks like an eye
- a small spot of pigment associated with sensitivity to light, found in many invertebrates
- A light-sensitive organelle of certain chiefly unicellular organisms, such as euglenas and some motile algae.
- A simple visual organ of certain invertebrates, consisting of a cluster of photoreceptor cells and pigment cells.
- A rounded eyelike marking, as on the wings of certain butterflies.
- Any of several fungal diseases that affect grasses and are characterized by oval lesions.
on a butterfly wing