I am pretty much sure that for native speakers the issue I am going to bring up might look as an uncalled question as they can easily figure out which form of a verbal part of speech should be used, be it a gerund, an infinitive, or a bare infinitive. However, it can be pretty much misleading for a foreigner because the same construction works differently with different words and I don’t see a logical explanation. For example:

  1. The purpose of this article is to analyze the issue…

  2. My hobby is reading.

    One may assume, and many foreigners really come to this conclusion, that it’s OK to switch the “gerund” and “infinitive” as the meaning will stay the same, that is:

  3. The purpose of this article is analyzing the issue… (same as 1 above)

  4. My hobby is to read. (same as 2 above)

However, as I was told, this assumption is erroneous.

Another example:
His task was watching after them. (not good)
His task was to watch after them.

Is there any principle which governs the choice of the right form in such cases?

2 Answers 2


(1) There is a grammatical / semantic term applied to verbs, semelfactive - occurring but a single time. This is the case with The purpose of this article is to analyze the issue but not with My hobby is reading, where a continuous aspect is obviously applicable. Contrast My intention is to read after supper.

(2) Many verbs catenate

(Appendix:English catenative verbs - Wiktionary) and take the bare infinitive, the to-infinitive, or the -ing form rather unpredictably (the article contains a useful list). Sometimes, the meanings differ:

I forgot to visit Aunt Molly. (I'll have to go next week instead.)

I forgot visiting Aunt Molly. (She reminded me that I had when she phoned yesterday.)

  • It makes sense in the case with "hobby" and "to analyze" However, the example with "task" could be seen with a continuous aspect, too. Does that mean that "His task was/is watching after them." is an acceptable sentence? Another thought regarding your example " My intention is to read after supper." What if to see it as his hobby. My (daily/constant) intention is to read (reading?) after supper. Whould it allow us to use the gerund in this case?
    – user1425
    Oct 24, 2012 at 22:42
  • Do I understand you to say that "The purpose", singular, constrains "analyze" to a semelfactive sense? Oct 24, 2012 at 23:16
  • @user1425: There are going to be arguable areas. Personally, I'd argue that task implies a one-off (though not necessarily of short duration) and thus prefer the to-infinitive construction here. Oct 26, 2012 at 19:32
  • @StoneyB: Not my meaning at all. Contrast the continuous (ie happening say now, but possibly not continuing eternally) aspect of For as long as I can remember, reading crime novels has been my favourite hobby. with *For as long as I can remember, the purpose of this article has been to analyze the issue. There is no continuous aspect in the second statement, but rather a perfective aspect - this is the purpose of the article; the issue is fixed (assuming one's analysis is correct) - the purpose of the article will not be subject to change. Edwin Ashworth Oct 26, 2012 at 22:22
  • @EdwinAshworth Thank you. I have encountered semelfactive only as a semantic property of specific verbs; this appears to attribute semelfactivity to the utterance and to derive it from the context. Oct 26, 2012 at 22:59

Another example illustrating the differnce between the -ing form of a verb and its to-infinitive form:

  1. I stopped to talk to Jane. This means that the speaker was moving from one place to another and stopped in order to talk to jane. The to-infinitive form (to talk) expresses the purpose of stopping.
  2. I stopped talking to jane. This means I no longer talk to her.

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