optional 

  1. 形容詞
非必須的, 隨意的
非強制的
可選擇的, 可自由選擇的

    同義字詞
discretionary,elective,voluntary

  2. 名詞
選修科目
/此名詞複數為"optionals"/

    
                        
    3. 
                                            

                

            

            
            

                

                
例句

                

                    
    
                                                    
  1. 
                                Fresh, clean water is not optional .                            
    2. 
                                                    
  2. 
                                No, sorry, massager is an optional extra.                            
    3. 
                                                    
  3. 
                                Some fees for optional services may apply.                            
    4. 
                                                    
  4. 
                                Past tense marking is optional in Singlish.                            
    5. 
                                                    
  5. 
                                A parking brake warning light was optional .                            
    6.