This is word used to describe a characteristic of a hypothesis. it means you are able to experiment to see how two variables may be related.

The word  theory is used to describe a characteristic of a hypothesis that can be experimented and altered in order to understand the effect of two variables and how they may be related.

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.