In scientific writing, it's actually essential that you repeat a word.
You need to repeat keywords.
Any words that are keywords in your paper, like the names of groups,
the names of variables, the names of instruments, the names of a disease,
you absolutely must repeat these terms throughout the manuscript.
You need to be consistent, do not substitute synonyms for
this keywords as this will lead to great confusion.
I see this all the time with my students they change the keywords through out
the manuscript, because they are worried about repeating themselves but
this leads to all through trouble.
I've had students come in and they're working on a particular disease and
they call the disease one thing and one place in the manuscript.
And then they call is something different in other places in the manuscript.
And I'm left thinking that they are talking about two different diseases.
Or imagine if you're comparing groups and
in one case you call those groups the obese group and the lean group.
But then elsewhere, because you're afraid to repeat yourself
you call them the heavier group and the lighter group.
That's problematic,
because now as the reader I'm asking myself, are these new groups?
Have you redefined the groups?
Have you rejiggered the categories?
It's absolute essential in scientific writing that you be consistent in
how you name those keywords.