- Used in the sense of not, to negate the meaning of the word to which it is prefixed.
- The prefix non- may be joined to a word by means of a hyphen, which is standard in British usage. In many cases, especially in American usage, non- is joined without a hyphen. (For example, nonbaseball is relatively common, but noncricket — referring to a primarily British sport — is rare.) Some non- words rarely or never use a hyphen (such as nonentity).
- Unlike un-, non- tends to suggest an absolute negation without the possibility of shades of comparison. For example, more unkind sounds quite natural, but more nonhelpful does not.
- Meaning "not" in phrases taken from Latin and some other languages, non is a separate word and is not hyphenated. Examples: non compos mentis, persona non grata.
- As non- is a living prefix, the list of words having the prefix non- is practically unlimited. It is particularly common in the sciences.
- Non- may be attached to nouns, verbs, adjectives or adverbs to negate their meaning.