少しも～ない【すこしも～ない】

少しも with a negative means "not at all", "not even a little". It goes in front of a negative verb or adjective and denies that there is any amount of the thing at all.

The predicate has to be negative. With an affirmative, 少しも does not mean "a little"; that is plain すこし少し.

• × 少しも分かる → 少し分かる

少しも, 全然 and ちっとも

All three mean "not at all" with a negative. 少しも is neutral and fits writing and polite speech. ぜんぜん全然 is the everyday word, and ちっとも is conversational and sounds irritated or disappointed.

In casual speech 全然 also turns up before a positive, as in ぜんぜん全然だいじょうぶ大丈夫. 少しも never does.

• × 少しも大丈夫 → 全然大丈夫