彼女は僕より２歳年下だ。
tbd
她比我年輕兩歲。
She is two years younger than I.
She is two years younger than me.
She's two years younger than me.
は
1. indicates sentence topic
2. indicates contrast with another option (stated or unstated)
3. adds emphasis
指示句子的主题；表示与另一选项（无论是否明确提及）形成对比；表示强调
より
1. than
2. rather than, instead of, over, above
3. from, out of, since, at, on (and after)
4. except, but, other than
5. more
更，更加