dairy >< diary

 dairy is related to milk.
  Eg. Dairy farm. He lives by running a dairy farm. (ఆవులు/గేదెల్ని పెంచుకుంటూ, పాల వ్యాపారం చేస్తారు)

  diary is a record of events. Some people write a diary very ritually.
  E.g. Many companies print diaries and gift them to their customers.