Would someone living on another planet speak English? Of course not. Given enough time (and maybe monkeys and typewriters) I could invent an alien language. Then I could teach it to my readers so that my characters could speak in their ‘native’ language. I think I might lose a reader or two along the way. Instead, my anjels speak English. If the book is translated into French, they will speak French. You could consider the whole thing a translation from anjel, no matter what language of Earth we are using.
Even so, there are elements of language that would jar the reader coming from an anjel. Idioms are banished. For instance, an anjel better not say “she is pulling my leg” unless someone is actually pulling her leg. She would not have the context to understand that phrase means that someone is teasing her with a little lie.
Anjels can use a language of Earth, but they cannot use a reference to Earth. Neither can the narrator. This severely limits the use of metaphor and simile. The planet where anjels live has little that is familiar to us. There are no dogs, ducks or Dodges. There are animals and birds; grass and trees. There are mountains and rivers and canyons.
So what do I call mountains, rivers and canyons? Mountains, rivers and canyons. The wind is the wind and rain is rain. A flying creature might be a bird, but it is certainly not a goose. Anjels have their own names for whatever uniquely inhabits their world. They have their own names for each other, so you will not read about Sue and Becky, rather you will get to know Lasa and Talaka.
Eliminating earthly references and severely limiting metaphor and simile builds a tight little box for a writer to work in. My writing mentor, Tom Trusky, taught me how important it is to do that and how it forces your mind into a creative space. Next time a bit more about Tom and why he might warn me not to blog a book.