1. Not accessible to direct observation

See also: imperceptible, unperceivable

• Sapindus drumondii
• Sapindus marginatus
• Sapindus saponaria
• Sapir
• sapless
• sapling
• sapodilla
• sapodilla family
• sapodilla plum
• sapodilla tree
• saponaceous
• Saponaria
• Saponaria officinalis
• urethritis
• urethrocele
• urethroscope
• urethrotome
• Urex
• Urey
• Urga
• urge
• urge incontinence
• urge on
• urgency
• urgent