The word carries the basic meaning of 'single' as opposed to 'double' or 'divided,' but in its New Testament usage it describes moral character. Jesus uses it to describe an eye that is 'clear' or 'healthy'—one that sees properly and lets in light, in contrast to an evil eye that is clouded or diseased. The multilingual evidence reveals an interesting nuance: Spanish 'sencillo' (simple, sincere) and English 'clear, healthy' both point to the moral dimension, suggesting unpretentious generosity and wholehearted devotion to God. The metaphor of the eye in Matthew 6 and Luke 11 connects physical sight to spiritual insight, where singleness of vision means undivided loyalty.