MAGNETIC COMPASS – A directional instrument, actuated by the Earth’s magnetic field

MAGNETIC NORTH - The direction to which a compass points. Magnetic north differs from true north because the magnetic fields of the planet are not exactly in line with the north and south poles. Observed differences between magnetic and true north is known as magnetic variation.

MAGNETIC POLE – One of the two geographic areas, north and south, where the Earth’s magnetic field enters or leaves the Earth.

MAINCHAINS - Heavy steel plates fastened to a ship's sides that anchor the rigging for the mainmast

MAINMAST - The tallest mast of the ship; on a schooner, the mast furthest aft.

MAINSAIL - The sail set on the mainmast.-the lowest square sail on the mainmast.

MAINSHEET - The line that controls the boom.

MAKE COLOURS – Hoisting the ensign at 8 a.m.

MAKE FAST - To attach a line to something so that it will not move.

MARINA - Commercial dock facility. Among the few places, under admiralty law, where certain forms of piracy are still permitted, most marinas have up-to-date facilities for the disposal of excess amounts of U.S. currency that may have accumulated on board ship, causing a fire hazard.

MARK – The fathoms of a lead line which are marked.

MARLINE – A small cord composed of two strands, loosely twisted, used for winding around rope and cable

MARLINESPIKE - A tool for opening the strands of a rope while splicing.

MARLINESPIKE SEAMANSHIP - A general term referring to the working of rope, cable, etc. Encompasses tying of knots, bends, lashing and other activities. Sailors, even modern day ones, often take great pride in their marlinspike seamanship. Even on modern missile cruisers, it is not unusual to see a Knot Board, made by a member of the crew, displaying many different kinds of knots, both useful and decorative.

MARRY THE GUNNER'S DAUGHTER - Old Navy nickname for a flogging, particularly when across a gun.

MAST - A spar placed vertically in a boat to hold up the sails.

MASTER  - The captain of a merchant ship.

MATE - A deck officer ranking below the master on a merchant ship.

MASTHEAD - The top of the mast.

MAYDAY – The international radiotelephone distress signal

MEASURED MILE - A course marked by buoys or ranges measuring one nautical mile.

MERCATOR – A chart projection

MERIDIAN – An imaginary line on the surface of the Earth joining the North and South poles

MESSENGER - A small line used to pull a heavier line or cable

MID-CHANNEL BUOY – A fairway buoy

MIDSHIP - Approximately in the location equally distant from the bow and stern.

MILE (NAUTICAL) - A relativistic measure of surface distance over water - in theory, 6076.1 feet. In practice, a number of different values for the nautical mile have been observed while under sail, for example: after 4 p.m., approximately 40,000 feet; in winds of less than 5 knots, about 70,000 feet; and during periods of threatening weather in harbor approaches, around 100,000 feet.

MINUTE – As an angle, 1/60 of a degree.  As time, 1/60 of an hour

MIZZEN - The shorter mast behind the main mast on a ketch or yawl. A fore-and-aft sail set on the mizzenmast

MIZZENMAST - The third mast from the bow or the mast aft of the mainmast in a sailing ship.

MONKEY’S FIST – A know worked into the end of a heaving line

MONOHULL  - A boat with one hull

MOORING - An arrangement for securing a boat to a mooring buoy or a pier.

MOORING - The act of bringing a boat to a complete stop in a relatively protected coastal area in such a fashion that it can be sailed away again in less than one week's time by the same number of people who moored it without heavy equipment and no more than $100 in repairs.

MOORING BUOY -A buoy secured to a permanent anchor sunk deeply into the bottom.