Which combining form denotes saliva?

• A. aut/o
• B. gastr/o
• C. sial/o
• D. somn/o

Answer: (C)

The key idea here is recognizing which combining form names a bodily substance. Saliva is represented by the combining form sial/o, coming from the Greek sialon meaning saliva. This form appears in terms about saliva or the salivary glands, such as sialadenitis (inflammation of a salivary gland) or sialolithiasis (salivary stone). The other options point to different concepts: aut/o means self, used in terms like autograft or autoimmune; gastr/o means stomach; somn/o means sleep. So sial/o is the combining form that denotes saliva.