关于“兴趣自学法语”用英语表达，综合多个来源信息整理如下：
一、核心表达
兴趣自学：self-study（强调自主学习）或on one's own（较少用）
法语：French（形容词/名词）
二、完整句子示例
- I am interested in self-studying French.
- She likes to learn French on her own.
动宾结构
- He takes interest in self-studying French.
- They are engaged in self-study of French.
短语表达
- Learning French out of interest.
- Self-study of French for personal enrichment.
三、补充说明
短语扩展： with a hobby（如：He learns French with a hobby） 
as a personal project（如：She did it as a personal project）
注意事项：
"On one's own" 更强调完全独立，而 "on one's interest" 则侧重因兴趣驱动，根据语境选择更贴切的表达。
建议优先使用 self-study of French作为标准表达，既符合英语习惯，又能准确传达“兴趣驱动的自主学习”含义。
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