The Alkynes 
The alkyne series is very similar to the alkane and alkene series. They all have at least one triple bond. Please note the fact that a single letter change results in a dramatic change in the structure of a compound.
Alkyne Formula
Ethyne  C2H2                                                                         Propyne C3H4

Butyne C4H6
                                   but-1-yne                                                                     but-2-yne
And the pattern continues just as it did for the alkanes and alkenes. The general formula of an alkyne is CnH2n-2. The triple bond prevents rotation but it also prevents the formation if cis and trans structures in the parent chain.
In the event a parent chain has both an alkyne and an alkene the alkyne is more important.
8 carbons long therefore an "oct". Has both alkene and an alkyne bonds. The alkyne is the most important therefore number so that it has the lowest possible number. Therefore we now have "3-yne" and an alkene at 5 and at 7. Therefore the full name would be oct-5,7-diene-3-yne.
All the other rules previously learned still apply.
           Go to Organic Alkenes and Akynes Nomenclature Worksheet