1.向…正式申请；向…要求：
The captain applied to headquarters for a transfer.
上尉向司令部请求调动.
2.专心致志于：
to apply one's mind (或oneself) to economic work
致力于经济工作
3.把…应用于；把(能力等)用于：
Scientific discoveries are often applied to industrial and agricultural production methods.
科学发现常被应用于工农业生产方法上.