I'm helping someone to write their academic paper. He wrote 'something is constant in one year.' But I feel the 'in one year' is a bit awkward. Do I need to change it? The meaning is that we are making an assumption that a certain variable remains constant in '1 year'. So it doesn't change during a certain year, while each year's value may be different.
We could also say "the value is constant throughout the year". It does sound better this way. Unless if that 1 year has to be specified. For example, if the tests were done for several years and then a description of one of the years is given, we could then say "the variable was constant in that one year", which would imply that it was always varying in the other years.