Study materials
Whole parts are missing from these sentences, yet the meaning stays clear.
Anna ordered the fish, and Ben the soup.
The verb ordered is left out.
Someone called, but I don't know who.
Only one word of the question is left.
Applicants must sign the form. Failure to do so delays the process.
Do so replaces the whole action.
This article explains the main condition for leaving words out, leaving out the verb in parallel clauses, a question word in place of a whole question, when leaving out does harm, and how do so, do it and do that replace an action.
The main condition
What is left out must be recoverable in only one way. If more than one reading is possible, it is better not to leave it out.
I know Anna better than Ben does.
I know Anna better than Ben knows her.
I know Anna better than I know Ben.
I know Anna better than I know Ben.
I know Anna better than Ben.
Both readings are possible.
So in comparisons the auxiliary is often kept on purpose. It costs one word and removes the ambiguity.
Dropping the verb in parallel clauses
When two clauses are built the same way, the verb in the second can be dropped. The rest of the second clause must match the first exactly.
Anna ordered the fish, and Ben the soup.
Subject and object, as in the first clause.
Taras went to Lviv, and Olha to Odesa.
Subject and place.
If the clauses are built differently, there is nothing to drop: Anna ordered the fish, and Ben was hungry. This kind of ellipsis is more usual in writing, while in speech the verb is more often repeated.
A question word instead of a question
Once the content of a question has been named, only the question word remains.
Someone called, but I don't know who.
Instead of who called.
They're moving, but nobody says where.
Instead of where they are moving.
She'll come back. The question is when.
Instead of when she will come back.
The question word stands alone. Adding an auxiliary makes a mistake: but I don't know when will she.
When leaving words out does harm
Leaving words out is justified only when the missing part can be rebuilt unambiguously.
| Case | Why | What to do |
|---|---|---|
| the verbs in the parts differ | the missing part does not fit the second | repeat the verb |
| two readings are possible | the reader does not know what to rebuild | keep the helping verb |
| the parts are built differently | there is nothing to drop | write it in full |
She has never been to Rome, and I haven't to Paris. → She has never been to Rome, and I have never been to Paris.
The parts differ, so the short form does not work.
Do so, do it, do that
These phrases replace a whole action.
| Phrase | Where it is heard | What it replaces |
|---|---|---|
| do so | formal, written text | the same action, often by the same doer |
| do it | neutral | a specific action with an object |
| do that | neutral, stressing that very thing | the action just named |
Applicants must sign the form. Failure to do so delays the process.
A formal text.
I need to call the bank. I'll do it after lunch.
Everyday speech.
Do so, do it and do that replace an action. For a state such as know or like, use the plain auxiliary: She knows the answer, and I do too.
Common mistakes
The first mistake is leaving words out where the clauses are built differently.
Anna ordered the fish, and Ben hungry. → Anna ordered the fish, and Ben was hungry.
The second clause does not repeat the first.
The second mistake is an auxiliary after the question word.
She'll come, but I don't know when will she. → She'll come, but I don't know when.
The question word stands alone.
The third mistake is do so for a state verb.
She knows the answer, and I do so too. → She knows the answer, and so do I.
Know is a state, not an action.
The first mistake shows if you restore what is missing. Ordered hungry makes no sense, so the verb has to be written. The second shows after the question word. If the question is shortened, the word stands alone. The third shows in the verb of the first part. Know is a state, not an action, so instead of do so people say so do I or I do too.