According to this, key value is divided by any fitting number, generally a prime number, and the division of remainder is utilized as the address for the record.
The choice of suitable divisor may not be so simple. If it is known that the file is to have n records, then we has to, assuming that only one record can be stored at a given address, have divisor n.
Also we might have a very large key space as compared to the address space. Key space refers to every possible key value. The address space possibly may not match in fact for the key values in the file. So, calculated address may not be unique. It is called Collision, that means
R(K1) = R(K2), where K1 = K2.
Two unequal keys have been calculated to have the simialr address. The keys are called as synonyms.
There are several approaches to handle the problem of collisions. One of these is to hash to buckets. A bucket is a space that can suggest multiple records.