The difference between Mast and Spar

Mast as a noun:

A tall, slim post or tower, usually tapering upward, used to support, for example, the sails on a ship, flags, floodlights, or communications equipment such as an aerial, usually supported by guy-wires.

Mast as a noun (naval):

A non-judicial punishment ("NJP") disciplinary hearing under which a commanding officer studies and disposes of cases involving those under his command.

Mast as a verb:

To supply and fit a mast to a ship

Mast as a noun:

The fruit of forest-trees (beech, oak, chestnut, pecan, etc.), especially if having fallen from the tree, used as fodder for pigs and other animals.

Mast as a verb (of swine and other animals):

To feed on forest seed or fruit.

Mast as a verb (agriculture, forestry, ecology, of a population of plants):

To vary fruit and seed production in multi-year cycles.

Spar as a noun:

A rafter of a roof.

Spar as a noun:

A thick pole or piece of wood.

Spar as a noun (obsolete):

A bar of wood used to fasten a door.

Spar as a noun (nautical):

Any linear object used as a mast, sprit, yard, boom, pole or gaff.

Spar as a noun (aeronautics):

A beam-like structural member that supports ribs in an aircraft wing or other airfoil.

Spar as a verb (obsolete, or, dialectal):

to bolt, bar.

Spar as a verb (transitive):

To supply or equip (a vessel) with spars.

Spar as a verb:

To fight, especially as practice for martial arts or hand-to-hand combat.

Spar as a verb:

To strike with the feet or spurs, as cocks do.

Spar as a verb:

To contest in words; to wrangle.

Spar as a noun:

A sparring session; a preliminary fight, as in boxing or cock-fighting.

Spar as a noun (mineralogy):

Any of various microcrystalline minerals, of light, translucent, or transparent appearance, which are easily cleft.

Spar as a noun (mineralogy):

Any crystal with no readily discernible faces.