mortarboard
Word family nounmortarmortarboard
College
mor·tar·board /ˈmɔːtəbɔːd $ ˈmɔːrtərbɔːrd/ noun [countableC] 
SECa black cap with a flat square top worn by members of some universities on formal occasions 学士帽，学位帽 →5 see picture at 见图 hat- from A to Z
- from cradle to grave
- from day to day
- from day to day/from minute to minute etc
- from door to door
- (from) door to door
- from downwards
- from ear to ear
- from father to son
- from hero to zero
- from hour to hour
- from house to house
- from left field
- from left to right
- (from) left to right
- from minute to minute
- from nowhere
- from one day to the next
- from-one-day-to-the-next
- from one moment to the next
- from on high
- from onwards
- from ... onwards
- from place to place
- from place to place/house to house etc