Noun

(uncountable) The property of being thick (in dimension).

(uncountable) A measure of how thick (in dimension) something is.

The thickness of the Earth's crust is varies from two to 70 kilometres.

(countable) A layer.

We upholstered the seat with three thicknesses of cloth to make it more comfortable to sit on.

(uncountable) The quality of being thick (in consistency).

Whip the cream until it reaches a good thickness .

(uncountable, informal) The property of being thick (slow to understand).

Noun

(en noun)

The overside or up-side of a flat object such as a table, or of a liquid.

*{{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)

, chapter=Foreword citation , passage=A very neat old woman, still in her good outdoor coat and best beehive hat, was sitting at a polished mahogany table on whose surface there were several scored scratches so deep that a triangular piece of the veneer had come cleanly away,

The outside hull of a tangible object.

*{{quote-magazine, date=2013-05-11, volume=407, issue=8835, page=80, magazine=(The Economist)

, title= The climate of Tibet: Pole-land , passage=Of all the transitions brought about on the Earth’s surface by temperature change, the melting of ice into water is the starkest. It is binary. And for the land beneath, the air above and the life around, it changes everything.}}

*{{quote-magazine, date=2013-07-20, volume=408, issue=8845, magazine=(The Economist)

, title= Welcome to the plastisphere , passage=[The researchers] noticed many of their pieces of [plastic marine] debris sported surface pits around two microns across.}}

(lb) Outward or external appearance.

:

*(Vicesimus Knox) (1752-1821)

*:Vain and weak understandings, which penetrate no deeper than the surface .

*

*:“A tight little craft,” was Austin’s invariable comment on the matron; and she looked it, always trim and trig and smooth of surface like a converted yacht cleared for action. ¶ Near her wandered her husband, orientally bland, invariably affable,.

The locus of an equation (especially one with exactly two degrees of freedom) in a more-than-two-dimensional space.

(lb) That part of the side which is terminated by the flank prolonged, and the angle of the nearest bastion.

:(Stocqueler)