nly recently did I realize that “friendly” is an odd word. No one thinks twice about phrases like “the friendly grocer” or “the friendly dog,” but the strangeness of “friendly” becomes apparent when we want to express, for example, that our dog exhibits friendliness in the way he wags his tail. Competent native speakers of English would recoil from “the dog wagged his tail friendly.” Chances are, they wouldn’t be too comfortable with “the dog wagged his tail friendlily,” but, technically, this is a perfectly good sentence. All the words are in the dictionary as the parts of speech required for this utterance.

In “friendly,” we have the rare adjective ending in ly, an ending most commonly found on adverbs. “Friendly” cannot be used as an adverb, but we can change the final y to i and affix the usual adverbial ending to yield “friendlily,” a word really in the dictionary, though one I must admit to never having used un-self-consciously.

A more natural sounding sentence would be “the dog wagged his tail in a friendly manner.” Alternatively, one might recast the sentence a bit to yield something like “the dog greeted us with a friendly wag of his tail.”

How rare is a word like “friendly”? After a little thought, I came up with the adjectives “comely” and “holy,” which have adverbial forms “comelily” and “holily,” respectively. I am hard pressed to devise credible sentences that use either of these adverbs, however. (“The priest behaved shamefully at the comedy club on open mike night, but he acted holily in church the next day,“ perhaps.)

Thinking about such unusual adjectives led me to check the Web for additional examples of adjectives ending in ly. There are more than I expected. It didn’t take long to compile the following list:

Of course, not all of these words have a corresponding adverbial form ending in lily, whether rare or not. (Other adverbs of this sort include “uglily,” “wilily,” and melancholily,” which is perhaps one of the more euphonious of these odd-sounding adverbs.) Some adjectives ending in ly are themselves also adverbs, such as “early,” “weekly,” “timely,” “kindly,” “sisterly,” “unseemly,” and “leisurely.” Others have no credible related adverb, largely because opportunities for their use are nearly inconceivable. This group includes “thistly” and “hilly.” “Sly” is unique in not having a final syllable sounding like “lee.” Its adverbial equivalent is either “slyly” or “slily,” either of which could be used without embarrassment.

Since most speakers prefer to avoid words so strange sounding that they seem made up, -lily adverbs are usually eschewed in favor locutions using “manner” (as suggested above), “fashion,” or “way”:

The dog wagged his tail in friendly manner.
The dog wagged his tail in a friendly fashion.
The dog wagged his tail in a friendly way.

On the other hand, you can amaze your friends by using “friendlily” instead.

— LED, 9/5/2009, rev. 9/15/2010