他吝啬到连生日礼物都舍不得给朋友买。

He was so miserly that he wouldn't even buy his friend a birthday gift.

miserly 是形容词，来自名词 miser（吝啬鬼、守财奴），加上后缀 -ly 构成形容词，表示"吝啬的、小气的"。这个词带有贬义色彩，形容一个人过分节俭甚至不愿为他人花钱。