2D

Abbreviation of two pence, tuppence (in pre-decimalisation currency, never used for 'two new pence').

Number-two; following after the first one with nothing between them. The ordinal number corresponding to the cardinal number two.

"He lives on Second Street."

Next to the first in value, power, excellence, dignity, or rank; secondary; subordinate; inferior.

Being of the same kind as one that has preceded; another.

"Residents of Texas prepared for Hurricane Harvey, which would in some ways turn out to become the second Hurricane Katrina."

Existing in two dimensions.

Not creating the illusion of depth.