He never had a truer friend than his sergeant in the army.
GPS systems can provide a truer basis for locating positions than celestial navigation.
Yes, truer is a word. In the definition of true in the Merrian-Webster, truer is an inflected form of true.
truer
truer, truest
A good way to use retentive in a sentence is... "How do you use the word retentive in a sentence?"
use it by saying- how can you use the word ebullient in a sentence?
Can you use the word concluding in a sentence? Done.
How do you use the word gerontology in a sentence?
How can you use the word infectious in a sentence
You can use the word Truss in a sentence like this.
Just use it! Or do you mean, can you use the word beheld in a sentence.
You can use an underscore to remove a word out of a sentence. It can be placed where the word was.
Since that is not a word I would not attempt to use it in a sentence.