Type Alias RelativeTimeFormatPart

RelativeTimeFormatPart:
    | { type: "literal"; value: string }
    | {
        type: Exclude<NumberFormatPartTypes, "literal">;
        unit: RelativeTimeFormatUnitSingular;
        value: string;
    }

An object representing the relative time format in parts that can be used for custom locale-aware formatting.

MDN.