What type of relationship involves people who don't share the same status?

The type of relationship which involves people who don't share the same status is vertical.
This exists everywhere - for example, in schools: there is a vertical relationship between students and teachers; or in business: there is a vertical relationship between employees and their employers. One party is above the other in status, thus making their relationship a vertical one. If they had the same status, it would be horizontal. 

Select the word from the list that best fits the definitionstates the the universe is expanding