音标：['ɒpʃәnl]
a. 可选择的, 随意的
【化】 选购的
在线英汉词典

optional的短语、例句：

optional adj that may be chosen or not, as one wishes; not compulsory 可选择的; 随意的; 非强迫的
optional subjects at school 学校的选修课
Formal dress is optional. 是否穿礼服自便.
The cassette player is an optional extra in this make of car, ie It will cost extra if one chooses to have it. 这种型号汽车如需盒式磁带唱机费用另计.