Ellipsis in comparative clauses

She earns more than he earns is grammatical. The verb phrase can be shortened further: She earns more than he does. The rule therefore does not require every repeated verb to be removed.

The compared degree or quantity inside the than-clause is a different matter. In an ordinary comparison, we do not repeat more there as part of another identical comparison. Two facts—she knows a lot; they know less—do not mechanically produce than they know more….

In theoretical grammar, comparative deletion refers to omitting the compared component; additional verb-phrase ellipsis is a separate process. This distinction helps avoid treating every long than-clause as incorrect.

For an ordinary lexical verb in the Present Simple, use do or does; in the Past Simple, use did. Make the remaining auxiliary agree with the subject and tense of the second clause itself.

If the second clause needs be, perfect auxiliary have, or a modal verb, retain the appropriate form. Do not replace every predicate with a universal do. Longer verb sequences sometimes allow different degrees of shortening if the required meaning remains clear.

Shorten repeated material, but retain what is contrasted: a participant, period, place, object, or modality. When comparing the present with the past, a remaining did or was often makes the time difference clearer.

Do not automatically carry a negative from the first clause into the second. Not as much as means a smaller quantity, not necessarily none at all. Do not turn a smaller amount into zero or inequality into equality.

When the second clause has an expressed finite verb, its subject takes the form he, she, I, we, or they: than he does, than I am. Him cannot fill this subject role before does.

Without an expressed verb, both than he and than him are possible. A subject-form pronoun without a verb sounds more formal or literary; an object-form pronoun is common in everyday language. Than he does is often a useful neutral way to make the structure explicit.

Do not label an object-form pronoun after than an error merely because you can mentally add a verb. A full subordinate clause and a short than-construction need not have the same structure.

In I trust Maya more than Leo, the short remnant Leo can be a second person doing the trusting or a second object of my trust. If the context does not resolve this, expand the part that makes the role clear.

Him does not guarantee a single interpretation either. In an ordinary conversational comparison, it can identify the person whose action is being compared, but after a transitive verb it can also be read as another object. In an important message, clarity matters more than minimum length.

When different properties or things are compared, the second component can be new information: height versus width, complaints versus thanks. Removing it changes the meaning.

In a special contrastive context, emphatic repetition of the same property is also possible. Neutral practice should therefore avoid rules such as adjectives are always forbidden after than. Detailed theoretical analysis of these constructions is unnecessary for ordinary editing.

Contractions in writing create a separate boundary: do not leave a final I'm instead of I am before an omitted predicative component. This is not a ban on all apostrophes: negative forms such as didn't are possible in the appropriate context.

First identify both sides and the feature being compared. Then check which words can be recovered without guesswork. Choose between a fuller clause, a remaining auxiliary, and a short noun phrase.

Finally, reread from the recipient's perspective: has the time reference changed, is the agent clear, and has a new object disappeared? A complex contrast may require more words. The goal is a clear comparison, not the shortest possible line.