sir, i dont understand how to choose the word root.can you please show me some more examples to name the compounds

In organic nomenclature, first rule is to find out the parent chain. while choosing the parent chain the following points must be kept in consideration:

The longest continuous carbon chain containing as many functional groups, double bonds, triple bonds, side chains and substituents as possible is to be selected as parent chain.

 

 

 

i) In the following molecule, the longest chain has 6 carbons. Hence the root word is "hex-". 

 

However the chain with more number of substituents (that with 3 substituents as shown in the following diagram) is to be taken as the parent chain.

 

Another example is as follows: There are two chains with 6 carbons. But the chain with the a double bond as shown in the diagram (II) is to be selected as the parent chain.