propos

1
à propos

• Adjective - appropriate, to the point "That's
  true, but it's not apropos.
• Adverb - at an appropriate time, opportunely
  "Fortunately, he arrived apropos.
• Preposition (may or may not be followed by of) -
  with regard to, speaking of "Apropos our
  meeting, I'll be late" "He told a funny story
  apropos of the new president."

2
à la carte   

• Definition - "on the menu"
• Sentence He decided to order á la carte instead
  of getting the special.

3
aide-de-camp 

• Definition - A military officer who serves as a
  personal assistant to a higher-ranking officer
• Origin - French - "camp assistant
• As the general inspected the troops, he was
  followed two paces behind by his aide-de-camp.

4
au gratin 

• Origin French -  "with gratings
• Definitions
• In French, au gratin refers to anything that is
  grated and put on top of a dish
• In English, au gratin means "with cheese.
• Sentence He ordered the potatoes au gratin
  because he loved the sharp Cheddar cheese on top.
  

5
au jus   

• Pronunciation oh
• Origin French - "in the juice
• Definition -   Served with the meat's natural
  juices
• Sentence He ordered the French dip sandwich
  with au jus for dipping.

6
bon appétit   

• Origin French - "good appetite"
• Definition - "Enjoy your meal
• Sentence The chef placed the gourmet dinner on
  the customers table and said, Bon appétit.