Parallel Form

If you want to express a series of ideas that are similar in importance, you have to make sure that the grammatical forms you use are consistent (parallel). This applies to the word, phrase and clause level. What does that mean?

Here is an example:

Not parallel:
The wolf had big eyes, shaggy fur, huge paws and was smiling in a wicked way.

Parallel:
The wolf had big eyes, shaggy fur, huge paws and a wicked smile.

As you can see, the first description suddenly changes form. Instead of continuing with adjectives (big, shaggy, huge) and nouns (eyes, hair, smile), the word forms change completely. They should be similar because they continue with the same idea.

Here are some more examples that show you how this works on all levels, for words, phrases (a group of words that doesn't have a subject or a verb) or clauses (a group of words that includes a subject and a verb).

Here are some examples:

Word and Phrase level

Not parallel:
Miss Hood was skipping, laughing and picked flowers on the way to her grandmother.

Parallel:
Miss Hood was skipping, laughing and picking flowers on the way to her grandmother.

In the above example, all the verb forms should be the same and be grammatically consistent with the auxiliary verb form "was".

More examples:

Not parallel:
She was on the way to see her grandmother who liked to drink wine, to eat chocolates and smelling the flowers her granddaughter brought her.

Parallel:
She was on the way to see her grandmother who liked to drink wine, to eat chocolates and to smell the flowers her granddaughter brought her.

Again, all verbs should have the same form and be preceded by "to". It is not always necessary to add "to" to every verb, but you definitely should not change the verb form from "to smell" to "smelling".

Not parallel:
The wolf fooled Miss Hood into believing he was her grandmother because he was wearing her nightgown, was sitting in her bed with a box of chocolates in front of him and the TV was on.

Parallel:
The wolf fooled Miss Hood into believing he was her grandmother because he was wearing her nightgown, was sitting in her bed with a box of chocolates in front of him and was watching TV.

Not parallel:
The wolf had swallowed the grandmother easily, quickly and without pain.

Parallel:
The wolf had swallowed the grandmother easily, quickly and painlessly.

Clauses

Not parallel:
After the ranger saved Miss Hood and her grandmother, he told them that they should never let a wolf into their house, that they should check visitors or pretend grandmothers for hairy paws and shaggy fur, and call 000 on their mobile phones in case of an emergency.

Parallel:
After the ranger saved Miss Hood and her grandmother, he told them that they should never let a wolf into their house, that they should check visitors or pretend grandmothers for hairy paws and shaggy fur, and that they should call 000 on their mobile phones in case of an emergency.

Another area where students often mix grammatical forms is when they are writing a list or dot points.

Here are some examples:

In the morning Miss Hood made a list of things to remember. These included:

To visit grandmother
Make sure to pick flowers on the way
Buying some more red wine
Remember to be careful of the wolf

A much better list would look like this:

Visit grandmother
Make
sure to pick flowers on the way
Buy
some more wine
Remember
to be careful of the wolf

As you can see, it is important to check for grammatical consistency and to make sure that all the words, phrases and clauses are parallel if you have a series of ideas that are all at the same level of importance.