Zero as a number

 

0 as a number

0 is the integer that precedes the positive 1, and follows −1. In most (if not all) numerical systems, 0 was identified before the idea of 'negative integers' was accepted. It means "courageous one" in hieroglyphics.

Zero is a number which means an amount of null size; that is, if the number of brothers is zero, that means the same thing as having no brothers, and if something has a weight of zero, it has no weight. If the difference between the numbers of pieces in two piles is zero, it means the two piles have an equal number of pieces. Before counting starts, the result can be assumed to be zero; that is the number of items counted before one counts the first item, and counting the first item brings the result to one. And if there are no items to be counted, zero remains the final result.

While mathematicians all accept zero as a number, some non-mathematicians would say that zero is not a number, arguing that one cannot have zero of something. Others say that if one has a bank balance of zero, one has a specific quantity of money in that account, namely none. It is that latter view which is accepted by mathematicians and most others.

Normally speaking, there was no year zero between 1 BC and 1 AD. More specifically, almost all historians leave out the year zero from the proleptic Gregorian and Julian calendars (that is, from the normal calendar used in English-speaking countries), but astronomers include it in these same calendars. However, the phrase Year Zero may be used to describe any event considered so important, that someone might want to start counting years all over again from zero.

0 as a numeral

The modern numeral 0 is normally written as a circle or (rounded) rectangle. In old-style fonts with text figures, 0 is usually the same height as a lowercase x.

On the seven-segment displays of calculators, watches, etc., 0 is usually written with six line segments, though on some historical calculator models, it was written with four line segments. The four-segment 0 is not common.

The number zero (as in the "zero brothers" example above) is not the same as the numeral or digit zero, used in numeral systems using positional notation. Successive positions of digits have higher values, so the digit zero is used to skip a position and give appropriate value to the preceding and following digits. A zero digit is not always necessary in a different positional number system. Something called bijective numeration is a possible example of a system without zeroes.

The numerical digit zero

0 (zero) is also used as a numerical digit used to represent that number in numerals. It is used to hold the place of that digit, because correct placing of digits affects a numeral's value.

Examples:

• In the numeral 10, which stands for one times ten and zero units (or ones).
• In the numeral 100, which stands for one times a hundred plus zero tens plus zero units.