Update

zero.md

@@ -9,8 +9,8 @@ Some properties of and facts about the number zero follow:
 - It is a [whole number](integer.md), a [natural number](natural_number.md), a [rational number](rational_number.md), a [real number](real_number.md) and a [complex number](complex_number.md).
 - It is **NOT** a [prime number](prime.md).
 - It is an additive identity, i.e. adding 0 to anything has no effect. Subtracting 0 from anything also has no effect.
-- Multiplying anything by 0 gives 0.
-- Its representation in all traditional numeral systems is the same: 0.
+- Multiplying anything by 0 gives 0, zero needs no units. Zero of anything is the same as zero of anything else: zero elephants is the same as zero frogs.
+- Its graphical representation in all traditional numeral systems is the same: 0. To distinguish it graphically from the letter *O* it's sometimes crossed over with a line, or a dot is put in the middle.
 - 0^*x* (zero to the power of *x*), for *x* not equal to 0, is always 0.
 - *x*^0 (*x* to the power of 0), for *x* not equal to 0, is always 1.
 - 0^0 (0 to the power of 0) is generally **not defined**! However sometimes it's convenient to define it as equal to 1.