at heart，by heart
这一组短语的涵义也各不相同。
At heart 的意思是“在心里”、“心底里”或“本质上”（from the heart，from the bottom of one's heart or essentially）。by heart 的意思是“背诵”、“熟记”（by rote；to learn so well that one can remember it perfectly）。请看下面例句：
That socialite is a rascal at heart．
那个知名人士实质上是个坏蛋。
A councillor should have the collective interest of society at heart．
议员应当关心大众的利益。
At heart，Mr．Lin does not approve your proposal．
林先生的心里并不赞同你的建议。
Mr．Wang looks stem，but he is kind at heart．
王先生看来严肃，但买质上他很仁慈。
I know this poem by heart．
我熟读／我能背诵这首诗。
I don't see the point of learning by heart all the dates in the history book！
我真不明白为什么要把历史书里所有的日期都要记下来！
请注意下列短语的意思：（跟前例 have something at heart相近）
in one's heart of hearts 在内心深处
take something to heart 认真考虑／关注某事
set one's heart on something 决心做／得到某事／物
cut（or touch）sb to the heart 触及某人痛处
one's heart is in something 把整个心放在某事上
( http://www.fwabc.org收集整理 )