Cardinality defines the numeric relationships between
occurrences of the entities on either end of the
relationship line. 
eg:
1)0:0
2)1:0
3)1:1
4)0:M
5)1:M
6)M:M

Cardinality is a property of a join that describes how many 
rows in one table match rows in another table. Cardinality 
is expressed as the minimum and maximum number of rows in a 
column at one end of a join, that have matching rows in the 
column at the other end of the join. 

The minimum and the maximum number of row matches can be 
equal to 0, 1, or N.

cardinality is mentioning the relatoin ship between the two 
columns participating in a join...eg: if cardinality is 1 
to n...for every column value in first table's field there 
exists many column values for the field in second table...

for every customer there may exists more than one address
(permanaent and temporary)

cardinality defines how many instances there for each uniqe
record in the related table.
the sole purpose of cardinality detection is to warn you of
possible loops

cardinality defines No of distinct instances that occur in 
a column

Ex:There is a column call Gender 

Gender
-------
Male
Female
Female
Male
female


Here cordinality of gender is 2