What verb form should you use after "consider" and "imagine"? Infinitive or gerund?

Consider can be followed either by a noun or a gerund (the "-ing" form of a verb used as a noun).

• They will consider the suggestions.
• I considered working.
• She considers going to the dentist.

Imagine can be followed by a noun, gerund, or that-clause.

• I can't imagine a larger dog than a mastiff.
• I can't imagine working harder.
• I can't imagine that she's telling the truth.

In both cases, when a verb directly follows consider or imagine, you should use the gerund form, not the infinitive:

• You should consider writing to him more often.
• It's easy to imagine winning the lottery, which is why I keep playing it.
  
  A gerund is the -ing form of a verb that acts as a noun. When certain verbs are followed by other verbs, the second verb needs to be in gerund form. Consider and imagine are two verbs that must be followed by a gerund if the second word is a verb.

Consider

Consider can be followed by a noun, a that-clause, or a gerund. Here are some examples.

Followed by a noun

• Please consider the facts.
• I have considered your offer.

Followed by a that-clause

• I wish my boss would consider that I have children when he makes the schedule.
• You should consider that she might not feel the same way about you.

Followed by a gerund

• Have you considered taking a painting class?
• I will consider going back to work when my kids are in school.

Consider cannot be followed by any other form of verb besides a gerund.

• Incorrect: He considered to change his major to biology.
• Correct: He considered changing his major to biology.

Imagine

Imagine functions like consider. It must be followed by a noun, that-clause, or gerund. It cannot be followed by any other verb form.

Followed by a noun

• Imagine a world with no internet.
• I like to imagine a future where I’m rich.

Followed by a that-clause

• She imagined that she was a princess.
• Let’s take a minute and imagine that you get the part.

Followed by a gerund

• Sometimes I imagine winning the lottery.
• He imagined running his own business since he was a boy.