The principal portion of a large land area. The term is used loosely to contrast a principal land mass from outlying islands and sometimes peninsulas.
Related Terms 
PILE CAP
A mass of reinforced concrete cast around the head of a group of piles to ensure that they act as a unit to support the imposed load.

PENNYWEIGHT
A unit of mass equal to 1/20 troy ounce or to 1.55517384 grams; the term is employed in the United States and in England for the valuation of silver, gold, and jewels. Abbreviated dwt; pwt.

PARALLEL AXIS THEOREM
A theorem which states that the moment of inertia of a body about any given axis is the moment of inertia about a parallel axis through the center of mass, plus the moment of inertia that the body would have about the given axis if all the mass of the body were located at the center of mass.

OUNCEDAL
A unit of force equal to the force which will impart an acceleration of 1 foot per second per second to a mass of 1 ounce; equal to 0.0086409346485 newton.

OUNCE
1. A unit of mass in avoirdupois measure equal to 1/16 pound or to approximately 0.0283495 kilogram. Abbreviated oz. 2. A unit of mass in either troy or apothecaries' measure equal to 480 grains or exactly 0.0311034768 kilogram. Also known as apothecaries' ounce or troy ounce (abbreviations are oz ap and oz t in the United States, and oz apoth and oz tr in the United Kingdom).

OPENCIRCUIT SCUBA
The simplest type of scuba equipment, in which all exhaled gas is discharged directly into the water and the utilization of gas is therefore equal to the mass exhaled.

ONSAGER RECIPROCAL RELATIONS
A set of conditions which state that the matrix, whose elements express various fluxes of a system (such as diffusion and heat conduction) as linear functions of the various conjugate affinities (such as mass and temperature gradients) for systems close to equilibrium, is symmetric when certain definitions are chosen for these fluxes and affinities.

NUCLEAR SNOW GAGE
Any type of gage using a radioactive source and a detector to measure, by the absorption of radiation, the water equivalent mass of a snowpack.

NEWTONIAN MECHANICS
The system of mechanics based upon Newton's laws of motion in which mass and energy are considered as separate, conservative, mechanical properties, in contrast to their treatment in relativistic mechanics.

MOISTURE CONTENT
The quantity of water in a mass of soil, sewage, sludge, or screenings; expressed in percentage by weight of water in the mass.
