Final answer:
The suffix -yl in a hydrocarbon's name indicates that the molecule contains an alkyl group, which is a substituent originating from an alkane with one fewer hydrogen. It denotes a branch in the molecular structure, and is used in systematic IUPAC naming to describe the components of organic molecules.
Step-by-step explanation:
In hydrocarbon nomenclature, the suffix -yl indicates that the group is an alkyl group, which is a substituent derived from an alkane by removing one hydrogen atom. These alkyl groups play an important role as branches attached to the main carbon chain, or parent hydrocarbon, in a molecule. For example, if a hydrocarbon chain has a methyl group (a one-carbon alkyl group) as a branch, it will be denoted as 'methyl' in the IUPAC name, hence the prefix methyl- attached before the parent hydrocarbon name. Multiple same alkyl groups are indicated with prefixes such as di-, tri-, and tetra- before the alkyl group name. In accordance with IUPAC naming conventions, these substituents are listed using their IUPAC names in alphabetical order, with their positions on the main chain indicated by numbers separated by commas, and connected to the name of the substituent without spaces by hyphens.