请问I will always remember my first day at school.句中的always为什么

always不是复数
是一个单词
always
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ad.
1.总是,经常
They always make fun of Mr.Smith.
他们总是嘲弄史密斯先生.
2.永远,一直
Children's Day is always the first of June.
儿童节一直是六月一日.
3.(动词用进行时)老是,一再
I'm always misplacing my glasses.
我老是将眼镜乱放而找不到.
4.(与can/could连用)随时
You can always resign if you feel unhappy.
如果你不满意,随时可以辞职.