badly

Badly is an English adverb formed from the adjective bad by the addition of the suffix -ly. It denotes that something is done in a poor manner, or to a low degree, or that a state or condition is severe. It is commonly used to modify verbs: “The team played badly,” “The engine ran badly in cold weather.” It can also modify adjectives or participles in phrases such as “badly damaged,” “badly needed,” or “badly designed,” to indicate that the quality is poor or the extent is significant. In comparison or emphasis, badly can intensify a claim: “The plan was badly flawed” or “She was badly hurt.”

In usage, badly is preferred in formal and standard writing for actions or states; informal speech sometimes features “bad” as a casual adverb, as in “He played bad,” though this is typically considered nonstandard in careful writing.

Etymology: the word is formed from the adjective bad using the common English adverb-forming suffix -ly; the sense of poor quality dates to Old English and earlier Germanic roots.

Related terms include poorly, which is often used in medical or evaluative contexts (e.g., poorly written, poorly treated), and ill, an older term that in modern usage mostly describes health rather than manner.