The definition of 30 is a number that follows 29 and precedes 31. It is an even composite number composed of two prime numbers multiplied together, namely 3 and 10. In mathematics, it has several important uses such as in the decimal system where it represents a value ten times greater than 20 (2×10).

In terms of its place value, 30 can also be seen as three tens or thirty ones; this means that when written out in full form it would read “thirty” rather than “three-zero”.

As for its ordinal form, which describes position within a sequence or list rather than magnitude (size), the word thirtieth should be used instead to describe something at the thirtieth point on said list/sequence.

30 itself holds special significance in some cultures due to being associated with certain events from their history such as Jesus turning water into wine at his first miracle during Passover which was held after he had been preaching for thirty years according to Luke 3:23–38; interestingly enough there are actually many other stories throughout various religions around similar themes involving figures reaching age 30 before achieving great things!