decimal point

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A dot written in a decimal number, as in 8.375, to indicate the place where values change from positive to negative powers of 10.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun arithmetic A point (.) used to separate the fractional part of a decimal from the whole part.
• noun arithmetic A decimal mark, any symbol used to separate the fractional part of a decimal from the whole part.
• noun proscribed A decimal place.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the dot at the left of a decimal fraction