Question: I cannot understand the morphology of the word retroviral. 

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> is "re" the prefix? 
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* I think the prefix might be retro, is that true?

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> is "al the suffix?
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* I am assuming that "viral" is the root, is that true

Answer: 
**retrovirus (noun) retroviral (adjective)** 

The prefix **"retro-"** has been added to **"virus"** because of the retrograde mechanism used for replication. 

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> * "Once inside the host cell cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards)." - from [Wikipedia](https://en.wikipedia.org/wiki/Retrovirus)
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[retrograde](https://www.merriam-webster.com/dictionary/retrograde) - "moving, occurring, or performed in a backward direction"

[retro](https://medical-dictionary.thefreedictionary.com/retro-) (pref.) "contrary to a usual or natural course or direction: retrograde."
As also stated in the other answer I see at the moment of writing here, the word retro in Latin means a movement backwards or a backward position, both in time and place. A quote from the Gospel is "Vade retro Satana" (Back away, Devil!), spoken by Jesus in the desert to the Devil who wanted to tempt him.

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> Go back, Satan!
>  An exhortation for Satan to be gone, often used in response to temptation. From a popular Medieval Catholic exorcismformula, based on a rebuke by Jesus to Peter in the Vulgate, Mark 8:33: vade retro me Satana |"step back from me, Satan!"|. The older phrase vade retro |"go back!"| can be found in Terence's Formio I, 4, 203. 
>  <https://glosbe.com/la/en/vade%20retro%20Satana>
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