数列:series of numbersRelative explainations: Examples:1. 第一万亿，第一兆可数数列中与一万亿相对应的序数The ordinal number matching the number one trillion in a series.2. 第九十在数列中与数字90相配的序数词The ordinal number matching the number90 in a series.3. 第十九在数列中与数字19相配的序数词The ordinal number matching the number19 in a series.4. 首项，末项比率或数列中第一个或最后一个项The first or last term of a ratio or a series.
