What is the meaning of observation?

noun

• The act of making and recording a measurement.
• The act of observing; taking a patient look.
  • synonyms: observance, watching
• A remark expressing careful consideration.
  • synonyms: reflection, reflexion
• Facts learned by observing.
  • usage: "he reported his observations to the mayor"
• The act of noticing or paying attention.
  • usage: "he escaped the notice of the police"
  • synonyms: notice, observance