It’s hard to imagine a less contentious or more innocent word than “and.”

But how to interpret that simple conjunction has prompted a complicated legal fight that lands in the Supreme Court on Oct. 2, the first day of its new term. What the justices decide could affect thousands of prison sentences each year.

Federal courts across the country disagree about whether the word, as it is used in a bipartisan 2018 criminal justice overhaul, indeed means “and” or whether it means “or.” Even an appellate panel that upheld a longer sentence called the structure of the provision “perplexing.”

The Supreme Court has stepped in to settle the dispute.

It’s the kind of task the justices — and maybe their English teachers — love. The case requires the close parsing of a part of a federal statute, the First Step Act, which aimed in part to reduce mandatory minimum sentences and give judges more discretion.