A1 immediately after the first and before any others第二（的），第二个（的）

A1 the position in which a person finishes a race or competition if they finish immediately behind the winner第二名（的）

B1 Second is used to show that only one thing is better, bigger, etc. than the thing mentioned仅次于第一（的）

B1 another另一（的）；又一（的）

happening only once out of every two possible times每隔一个（的）

B1 after the first and before any others第二（的），第二个（的）

B2 also secondly used to introduce the second thing in a list of things you want to say or write第二；其次

A2 [ C ] abbreviation sec., s a short unit of time that is equal to a 60th of a minute秒

B1 [ C ] a very short period of time片刻；瞬间

[ S ] the second person or thing to do or be something, or the second person or thing mentioned第二个；第二名

[ C ] specialized mathematics the smallest unit used for measuring an angle秒（最小角度单位）

C2 [ C ] a product that is sold cheaply because it is damaged or not in perfect condition残次品

[ C ] a person who takes care of someone who is fighting in a boxing competition or, in the past, in a duel (= organized fight)（拳击比赛或旧时决斗中的）助手

[ U ] also second gear in a vehicle, the gear that combines power with limited speed and is used when increasing or reducing speed（车辆的）二挡

[ C ] UK also second-class degree an undergraduate degree from a university in the UK and some other countries that is a good degree but not the best possible（英国大学中的）第二等学位

[ C usually singular ] informal → second base （同 second base）

to make a formal statement of support for a suggestion made by someone else during a meeting so that there can be a discussion or vote附议；赞成

to send an employee to work somewhere else temporarily, either to increase the number of workers or to replace other workers, or to exchange experience or skills（临时）调任，调派