the best and most expensive seats or accommodation on a train, ship, etc. 头等座位（或车厢、舱等）◆You can upgrade to first class for €50. 你花 50 欧元就能升级乘头等舱。◆first-class travel 乘头等舱旅行➡business class
in the UK, the class of mail that is delivered most quickly 第一类邮件（在英国投递得最快的邮件）◆First class costs more. 第一类邮件的邮资较高。◆A book of first-class stamps, please. 请来一本快信邮票。
in the US, the class of mail that is used for letters and cards 第一类邮件（在美国用於投递信件和明信片）