I have wondered about how to make the words silly, ugly, friendly, lively, etc. into adverbs, so I researched in the Internet. I found many different answers, so I tried checking Oxford Dictionaries.
However, Oxford Dictionaries still gave me two answers:
-
this is from Oxford Dictionaries’ online grammar reference, “forming adverbs” page
Adjectives that end in -ly, such as friendly or lively, can’t be made
into adverbs by adding -ly. You have to use a different form of words,
e.g. ‘in a friendly way’ or ‘in a lively way’ instead - from the dictionary entries: there are results from typing
sillily, uglily, friendlily, livelily into Oxford Dictionaries’
website (online dictionary)
That’s quite an obvious contradiction from one of the most famous dictionary providers of the world!
So, are the words sillily, uglily, friendlily, livelily, etc. valid English?
Note: I already saw the “comparative and superlative adverbs” question that asked about the word sillily but I don't see any sources in there that are trustworthy enough (compared to oxford dictionaries), so I'm asking a new question.
EDIT: I've already reported the mistake to Oxford Dictionaries. They said that those words are valid (although rare) and it's a mistake in the reference, They say they will get it fixed soon.
Best Answer
If you use the real OED, you will find all these with no trouble:
So there is clearly ample evidence that this sort of thing exists.
Here in more detail is the OED entry for sillily:
So it has clearly been around for a long time.
That should answer your question about whether sillily is “valid English”. Sure, you may not care for it, but it is unquestionably an English word of long-standing use.