Avoiding repetition with do
Definition
A form of do can replace a previously mentioned verb or verb phrase when the missing meaning is clear from context. The substitute form carries the required tense and subject agreement.
Examples
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Nora works harder than I do.
Do replaces work in the comparison.
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I enjoyed the concert, and Leo did too.
Did replaces enjoyed the concert.
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Mina does not travel much, but her parents do.
The final do replaces travel much.
Substitution do vs. emphatic do
Leo plays chess, and I do too.
Do replaces the repeated verb phrase play chess.
I do enjoy chess.
Do strengthens the positive statement; it does not replace an omitted phrase.
Substitution do stands alone for recoverable content. Emphatic do is followed by the base form of the main verb.
Repeat an existing auxiliary instead of adding do
When the first verb phrase already contains an auxiliary or modal, the corresponding auxiliary normally carries the substitution.
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Mina can swim, and I can too.
The modal can replaces can swim.
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Ravi has finished, and Jo has too.
The perfect auxiliary has replaces has finished.
Common mistakes
Nora works harder than I does.
Nora works harder than I do.
The substitute auxiliary agrees with its own subject: I do, not I does.
I liked the film, and Sara did liked it too.
I liked the film, and Sara did too.
In substitution, did replaces the full repeated verb phrase rather than combining with its past-tense verb.
Quick check
Question 1 of 3
Which sentence correctly avoids repeating the verb phrase?
Do agrees with I and replaces cook.Which sentence uses did as substitution rather than emphasis?
In the first sentence, did stands for the repeated phrase called the office.Which sentence correctly repeats a modal auxiliary?
Because the original phrase contains can, the modal itself carries the substitution.Nice work — you've completed the quick check.
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