English English language Expression Language Linguistics Usage Writing

Complementary remarks

Q: I teach writing to foreign students and was asked a question that I just cannot answer. Both of these sentences are normal English: “I was happy being alone” … “I was happy to be alone.” But only the first of these is normal: “I became [or got] lonely being alone” … “I became [or got] lonely to be alone.” What’s wrong with that last sentence?

A: Your question has to do with adjectives and their complements—that is, the words or phrases that complete them. In this case, you’re attempting to complement the adjectives “happy” and “lonely” with two different phrases: one formed with a gerund or “-ing” participle (“being alone”), and the other with a “to” infinitive (“to be alone”).

As any native speaker of English would know immediately, the “happy” sentences work with both complements, but the “lonely” sentences don’t. “I got lonely to be alone” doesn’t sound like normal English.

This is because “lonely” is not among adjectives that can invariably be complemented by an infinitive. If you replace “lonely” with “afraid,” the original examples work: “I became [or got] afraid being alone” … “I became [or got] afraid to be alone.”

We wish we could tell you that there’s a predictable pattern here—that certain types of adjectives can always be complemented by both participles and infinitives, while other types are always restricted to one or the other.

Unfortunately, no clear pattern emerges. Different adjectives simply act differently in different contexts.

For instance, with another subject and another verb, those “lonely” sentences work with both complements: “It is lonely being alone” … “It is lonely to be alone.” (There “it” is a dummy subject; the real subject is the complement: “Being alone is lonely” … “To be alone is lonely.”)

While we can’t give you a rule about all this, we can make a few broad observations.

Dozens of evaluative adjectives (like “educational,” “interesting,” “lovely,” “pleasant,” etc.) can be used with either “to” infinitives or “-ing” participles if the subject is a dummy “it” and the verb is a form of “be” (like “is,” “was,” “might have been,” and so on). With adjectives like these, the complements are pretty much interchangeable: “It was lovely to see you” … “It was lovely seeing you.”

Many adjectives that modify a subject, and that have to do with the subject’s attitude or capabilities, are often complemented by infinitives. These include “able,” “afraid,” “anxious,” “bound,” “delighted,” “determined,” “eager,” “happy,” “hesitant,” “liable,” “likely,” “quick,” “reluctant,” and “unwilling.” (Example: “The pianist was delighted to perform.”)

Some of those adjectives can also be complemented by “-ing” participles if a preposition is added, like “about” (as in “delighted about performing”), or “in” (“quick in replying”).

Still other adjectives, ones that refer to the experiencing or doing of something rather than to the thing itself, can be complemented by “to” infinitives. In a sentence like “This piece is difficult to perform,” the adjective “difficult” refers more to the performing than to the piece. These adjectives include “boring,” “delicious,” “difficult,” “easy,” “enjoyable,” “hard,” “impossible,” “tough,” and “tiresome.”

Adjectives that are usually complemented by “-ing” participles are much less numerous than the other kind. Among them are “busy,” “pointless,” “useless,” “worth,” and “worthwhile.” For instance, we can say, “She’s busy eating,” but not “She’s busy to eat.

As for “busy,” notice what happens when we modify the adjective with “too”—both complements work: “She’s too busy eating” … “She’s too busy to eat.” Completely different meanings! This is because “too busy eating” implies a missing element—“… to do [something else].”

Some adjectives that are usually complemented by infinitives—like “absurd,” “annoying,” “awkward,” “fortunate,” “happy,” “logical,” “odd,” and “sad”—can be complemented with participles as well.

Here a point should be made. Sometimes the choice of adjective complement—infinitive or participle—makes no difference in meaning, especially if the subject is the dummy “it.” (Examples: “It’s exhausting to cook for twenty” … “It’s exhausting cooking for twenty.”)

But sometimes a different complement produces a different meaning. “He was happy to carry your suitcase” does not mean “He was happy carrying your suitcase.” Similarly, “I became afraid to be alone” is not the same as “I became afraid being alone.”

This is also true of verbs with these complements or objects. For instance, “I stopped to think” does not mean “I stopped thinking,” and “I remembered to call” does not mean “I remembered calling.” We’ve written several posts, most recently in 2019, about verbs that can have infinitives or gerunds or both as their objects or complements.

With verbs, too, linguists have found no clear pattern that could help a foreign student predict which types work with gerunds, or with infinitives, or with both. As we wrote in 2014, there are only broad outlines that don’t work reliably in all cases.

You can find more on this subject in The Cambridge Grammar of the English Language, by Rodney Huddleston and Geoffrey K. Pullum (pp. 1246, 1259), and A Comprehensive Grammar of the English Language, by Randolph Quirk et al. (pp. 1224, 1230-31, 1392-93).

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