Meaning

• Substance, material.

• A condition, subject or affair, especially one of concern.

  "What's the matter?;   state matters"

• An approximate amount or extent.

  "I stayed for a matter of months."

• The essence; the pith; the embodiment.

• Inducing cause or reason, especially of anything disagreeable or distressing.

• Pus.

Meaning

• To be important.

  "Sorry for pouring ketchup on your clean white shirt! - Oh, don't worry, it does not matter."

• (in negative constructions) To care about, to mind; to find important.

• To form pus or matter, as an abscess; to maturate.