Core Grammar #4: Mixed Sentences

The Pieces Just Don’t Fit Together

Two different problems can be called "Mixed Sentences." In both cases something in the first part of the sentence just does not fit with something in the last part of the sentence.

The basic definition of a mixed sentence is that it began in one direction, then switched to another direction without any warning. This is why mixed sentences are confusing.

Problem #1: The grammar doesn’t fit together.

This is a sentence

As I said in Core Grammar #2 (What Is a sentence?), a sentence is a set of words which contains:

  1. a subject (what the sentence is about, the topic of the sentence)
  2. a predicate (what is said about the subject)

Some words and some word groups are not eligible to be subjects:

Often the problem is that a word or two got left out, and careful proofreading (perhaps with reading aloud) will point out the problem:

The Topic Comment Sentence

You will not find much discussion of this one in grammar textbooks because it is a non-English structure. It starts by defining a topic, then (usually after a comma) gives a subject and a predicate:

The usual repair is to simply delete the extra pronoun which is restating the subject:

NOTE: In addition to being ungrammatical, the topic comment sentence is a very strong low-status marker.

Problem #2: The content doesn’t fit together.

A computerized grammar checker might catch the first sort of mixed sentence, but it will not catch the ones where the logic is fouled up:

Again, thoughtful proofreading is your best defense.

Is when… Is where…

Informal (and wordy) writing uses these phrases where a simple is would work much better. Here's why:

These do not work:

Better, less wordy, and more straightforward ways to write those sentences would be:

More Information:

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Revised 7/17/22 • Page author: Curtis Allen • e-mail: