| Name | # Files | Name | # Files | Name | # Files | ||
|---|---|---|---|---|---|---|---|
| ufo | 4 | uhf | 2 | ukraine | 3 | ||
| ulcer | 2 | ultrasonic | 2 | ultrasound | 3 | ||
| ultraviolet_radiation | 2 | umbilical_cord | 2 | unconscious | 2 | ||
| unemployment | 3 | unicorn | 2 | union_flag | 2 | ||
| unit | 2 | united_kingdom | 3 | united_nations | 3 | ||
| universe | 2 | university | 2 | unleaded_petrol | 2 | ||
| uranium | 2 | uranus | 3 | urbanization | 2 | ||
| urinary_system | 2 | urine | 2 | uruguay | 3 | ||
| usa | 4 | ussr | 3 | uterus | 2 |