What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Common Wrong Answers
“Time”
Time is a concept that applies to all the mentioned units (seasons, seconds, centuries, minutes), but it is not a specific element that differentiates these units from decades, years, or days.
“Numbers”
While numbers can be represented in all the mentioned units, they do not specifically appear in the words 'seasons', 'seconds', 'centuries', and 'minutes' in the same way the letter 'n' does.
“Letters”
Although letters are part of all words, the answer is specifically the letter 'n', and the guess 'letters' does not pinpoint the unique characteristic that differentiates the words in the riddle.
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