Multi-branched alkanes:

 If there is excess than one alkyl substituent available in the structure then the substituents are named in alphabetical order, again numbering from the end of the chain nearest the substituents. The structure in below diagram is 4-ethyl-3-methyloctane and not 3-methyl-4-ethyloctane.

If a structure has similar substituents, after that the prefixes di-, tri-, tetra-, et cetera are employed to present the number of substituents. For instance, the structure in below figure is termed as 2,2-dimethylpentane and not 2-methyl-2-methylpentane..

Figure:  4-Ethyl-3-methyloctane.