gerund/infinitive

[wowenglish1]

I wonder if there is any difference between "1" and "2".

1. His habit is to bite his nails.
2. His habit is biting his nails.

[jlinger]

I would suggest that the second sentence is either wrong, or at least misleading. His habit is the subject, is biting is the verb. But really, is his habit biting, or is he biting? It is his habit to bite his nails. He bites, his habit does not bite. Habits do not do anything; they cause you to do something.

I believe that using the infinitive here helps to make that rather narrow distinction. Otherwise, when you use the -ing word, it is confused with the present participle (is running, is biting), rather than the noun (gerund) that you intend.

[Barb_D]

His habit - subject
is - verb
biting his nails - gerund, serving as a noun, acting as the predicate nominative.

The verb isn't "is biting" but simply "is."

[jlinger]

That was my point, Barb - I agree with you. But the construction can be interpretted my way:
His habit - subject
is biting - verb
his nails - object
... and that's why I object to it. Unclear. Habits don't bite.

[Barb_D]

Okay - but while it can be momentarily ambiguous, I can't agree that it's wrong.

I don't find either of the originals particularly natural. He has a bad habit: biting his nails. He has the bad habit of biting his nails. He bites his nails. What a bad habit!