Scarcely and hardly
These words are followed by when or before, not than.
- Hardly had I entered the room when a strange creature ran out. OR Scarcely had I entered the room when a strange creature ran out. (NOT Hardly had I entered the room, than …)
No sooner is followed by than, not when
- No sooner did she complete one project than she started working on the next.
As you can see, the adverbs hardly, scarcely and no sooner are all negative expressions. When a negative expression comes at the beginning of a sentence, we use inverted word order. That means the auxiliary verb comes before the subject.
These adverbs can also go in mid-position. In that case, we use normal word order.
- I had hardly entered the room when a strange creature ran out.
- I had scarcely solved one problem before another cropped up.
Not only…but also
This correlative conjunction is often confused. When using not only… but also, you must make sure that both parts of this conjunction go before words of the same parts of speech.
- The controversy not only damages our image but also decreases investor confidence.
Here not only and but also go before two verbs.
- She was not only arrogant but also rude.
Here not only and but also go before two adjectives.
Lest
The conjunction lest is not very common in modern English. This word has a negative meaning. Therefore, it should not be used with not. The only auxiliary verb that can follow lest is should.
- Work hard lest you should fail. OR Work hard lest you fail. (NOT Work hard lest you should not fail.)
The same idea can be expressed using the expression or else.
- Work hard, or else you will fail.
- Leave on time, or else you will miss the train.