Definitions of in:

• noun:   a unit of length equal to one twelfth of a foot
• noun:   a rare soft silvery metallic element; occurs in small quantities in sphalerite
• noun:   a state in midwestern United States
• adjective:   currently fashionable

  Example: "The in thing to do"

• adverb:   inside an enclosed space
• adverb:   to or toward the inside of

  Example: "Come in"

• name:  A female given name (rare: 1 in 33333 females; popularity rank in the U.S.: #1979)
• name:  A surname (very rare: popularity rank in the U.S.: #21503)