1
30 is [predicate]
作为基数名词，30被视为单数，谓语动词用单数形式。
30 is an even number.
30是一个偶数。
三十
先理解核心含义，再看它在真实句子里的用法。
三十
the cardinal number 30
30 is an even number.
30是一个偶数。
十和三的乘积的基数
the cardinal number that is the product of ten and three
The number 30 appears on the back of his jersey.
数字30出现在他的球衣背面。
She circled 30 on the calendar to mark the deadline.
她在日历上圈出了30，以标记截止日期。
He counted to 30 before starting the race.
他开始赛跑前数到了30。
作为基数名词，30被视为单数，谓语动词用单数形式。
30 is an even number.
30是一个偶数。
表示年龄时，30前不加冠词，且turn后直接跟数字。
She turned 30 last week.
她上周满30岁了。
The child can count to 30.
这个孩子能数到30。
Not this
I am thrity years old.
Use this
I am thirty years old.
拼写错误：'thirty'的正确拼写是't-h-i-r-t-y'，不是'thrity'。
Not this
I have thirty of apples.
Use this
I have thirty apples.
数量词用法错误：当数字直接修饰可数名词时，不需要加'of'。例如，'thirty apples'是正确的，而'thirty of apples'是错误的结构。
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Dictionary facts from ECDICT.