In English grammar, a flat adverb or bare adverb is an adverb that has the same form as a related adjective. It does not end in -ly, e.g. "drive slow", "drive fast". A flat adverb is sometimes also called simple adverb.
For most bare adverbs, there exists an alternative form ending in -ly (slowly), but this form does not exist for some bare adverbs (e.g. fast, soon, straight, tough, far), sometimes this form has a different meaning (hardly, nearly, cleanly, rightly, closely), and sometimes this form is not used for certain meanings (sit tight, sleep tight). In addition, the ending -ly is also found on some words that are both adverbs and adjectives (e.g. friendly) and some words that are only adjectives (e.g. lonely).
Flat adverbs were once quite common but have been largely replaced by their -ly counterparts. In the 18th century, grammarians believed flat adverbs to be adjectives, and insisted that adverbs need to end in -ly. According to the Merriam-Webster Dictionary, "It's these grammarians we have to thank for ... the sad lack of flat adverbs today".
Despite bare adverbs being grammatically correct and widely used by respected authors, they are often incorrectly stigmatized. There have been public campaigns against street signs with the traditional text "go slow" and the innovative text "drive friendly".
- Garner's Modern American Usage, p. 897
- O'Conner, P.T.; Kellerman, S. (2009). Origins of the Specious: Myths and Misconceptions of the English Language. Random House Publishing Group. p. 30. ISBN 9781588368560.
- Working with Words: An Introduction to English Linguistics
- "Drive Safe: In Praise of Flat Adverbs" with Emily Brewster, part of the "Ask the Editor" series at Merriam-Webster.com
- Flat Adverbs Are Flat-Out Useful
- Merriam-Webster, Inc (1998). Merriam-Webster's Manual for Writers and Editors. Merriam-Webster. p. 373. ISBN 9780877796220.
- When Adverbs Fall Flat, including list of the most common bare adverbs