When to use cis or trans?

[Grace_Stevenson_1A]

How do you know when to use cis or trans at all? Like I know what the difference is between the two but how do you know when to introduce one of those two terms at all? For example for this homework question (28) I would have just called it 3,4,6 trimethyl 3-octene but the correct name is adding a trans to the beginning. Thank you!

[Sarah_Heesacker_3B]

You use cis and trans (or the E,Z naming system) if there is a double or triple bond. When there are single bonds, they can rotate freely so there is no different name for the structures when they rotate. However, when there are pi bonds like in double bonds, they cannot rotate. This gives two different structures: cis and trans.
I hope this helps.