What is the meaning of in?

noun

• A unit of length equal to one twelfth of a foot.
  • synonyms: inch
• A rare soft silvery metallic element; occurs in small quantities in sphalerite.
  • synonyms: indium, atomic number 49
• A state in midwestern United States.
  • synonyms: Indiana, Hoosier State

adjective

• Holding office.
  • usage: "the in party"
• Directed or bound inward.
  • usage: "took the in bus"; "the in basket"
• Currently fashionable.
  • usage: "the in thing to do"; "large shoulder pads are in"

adverb

• To or toward the inside of.
  • usage: "come in"; "smash in the door"
  • synonyms: inwards, inward