Pump

A pump comprising:

• a vibrating plate;
• a piezoelectric body connected to a first main surface of the vibrating plate;
• a cover including a top plate and a side wall,
• the top plate facing a second main surface of the vibrating plate, which is on the opposite side from the first main surface of the vibrating plate,
• the top plate having an opening part, and
• the side wall being connected to an outer peripheral portion of the top plate so as to surround a space between the top plate and the vibrating plate;
• a support portion connected to the side wall and supports an outer periphery of the vibrating plate;
• an opening between the side wall and the vibrating plate;
• and
• a protrusion on any one out of the top plate, the side wall, and the vibrating plate so as to protrude into the space;
• wherein the protrusion is in between the opening part of the top plate and the side wall in a cross section viewed in a direction parallel to the second main surface of the vibrating plate.