English Translation
I’d like to help you if I can.
Are there any differences between мочь and смочь ?
Мочь.
Past tense: Она могла помочь мне (She could help me) – did she help? We don’t know. She had a possibility.
Смочь
Past tense: Она смогла помочь мне (She managed to help me) – did she help? Yes, she definitely did.
The difference is huge. Смочь is a perfective aspect of a verb. While you would use tenses in English to convey the same meaning, Russian simply has two aspects of a verb.
As it is usually with imperfective and perfective verbs, мочь is for a continuous action, and смочь is for a completed action.
This is the verb “to be able”, so a continuous state of being able to do something describes a theoretical capability to do something, and a completed action describes a capability that was acted upon.
Examples in the past tense:
Она могла прочитать эту книгу — She could read this book. (We think that she could, but we are not saying whether she actually did. Maybe she did and maybe she didn’t.) Она cмогла прочитать эту книгу — She could read this book. (And actually did. This could also be translated as “She managed to read this book”.)