体内

Traditional form:

體內

Pinyin (reading):

tǐnèi

Definitions:

• within the body
• in vivo (vs in vitro)
• internal to

Characters:

• 体 - body; group, class; form, style, system
• 内 - inside

Traditional characters:

• 體 - body; group, class; form, style, system
• 內 - inside