A mechanical seal is a device that helps join systems or mechanisms together by preventing leakage (e.g. in a pumping system), containing pressure, or excluding contamination. The effectiveness of a seal is dependent on adhesion in the case of sealants and compression in the case of gaskets.
A stationary seal may also be referred to as ‘packing’.
Induction sealing or cap sealing
Bodok seal, a specialized gas sealing washer for medical applications
Bonded seal, also known as Dowty seal or Dowty washer. A type of washer with integral gasket, widely used to provide a seal at the entry point of a screw or bolt 
Bridgman seal, a piston sealing mechanism that creates a high pressure reservoir from a lower pressure source
Compression seal fitting
Gasket or Mechanical packing
O-ring boss seal
Hose coupling, various types of hose couplings
Inflatable seal Seals that inflate and deflate in three basic directions of operation: the axial direction, the radial-in direction, and the radial-out direction. Each of these inflation directions has their own set of performance parameters for measurements such as the height of inflation and the center-line bend radius that the seal can negotiate. Inflatable seals can be used for numerous applications with difficult sealing issues.
Labyrinth seal A seal which creates a tortuous path for the liquid to flow through
Rotating face mechanical seal
Radial shaft seal
Trap (plumbing) (siphon trap)
Stuffing box (mechanical packing)
Dry gas seal