1.N-SING 单数名词（学科等的）基础知识，入门 The ABC of a subject or activity is the parts of it that you have to learn first because they are the most important and basic.

【搭配模式】：Nofn

2.N-COUNT 可数名词字母表（儿童识字、写字、拼词用的全部字母） Children who have learned their ABC or their ABCs have learned to recognize, write, or say the alphabet.

【搭配模式】：poss N

【STYLE标签】：INFORMAL 非正式