-ly

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Like; resembling; having the characteristics of: sisterly.
2. n. Recurring at a specified interval of time: hourly.
3. n. In a specified manner; in the manner of: gradually.
4. n. At a specified interval of time: weekly.
5. n. With respect to: partly.

Century Dictionary and Cyclopedia

1. An obsolete form of lie .
2. A common adjective suffix, forming, from nouns, adjectives signifying ‘of the form or nature of’ or ‘like’ the thing denoted by the noun: as in manly, womanly, godly, lordly, princely, of the nature of, like, or suited to a man, woman, etc.; bodily, earthly, daily, weekly, monthly, yearly, etc., belonging to or being of the body, the earth, a day, etc.; lovely, heartly (obs.), etc. Such adjectives, implying ‘like,’ are often accompanied by more definite adjectives in -like: as, manlike, woman-like, etc. The suffix is also used with some adjectives, as goodly, lowly, etc., and with some verbs, as comely, seemly, etc. They are usually accompanied by adverbs now of the same form. See -ly .
3. A common adverbial suffix, forming from adjectives adverbs signifying ‘in a manner’ denoted by the adjective: as, quickly, slowly, coldly, hotly, etc., loudly, harshly, etc. It is the most common adverbial suffix. In adverbs from nouns, as manly, womanly, etc., the adverb has the same form as the adjective in -ly , from which it is derived. The suffix is sometimes used with adjectives in -ly , as in seemlily, surlily, godlily, etc. Its use with primary adjectives, with no current adjective in -ly intervening (quickly, etc.), is more recent, but is now the prevalent one.

Wiktionary

1. n. Used to form adjectives from nouns, the adjectives having the sense of "like or characteristic of what is denoted by the noun".
2. n. Used to form adverbs from adjectives.

GNU Webster's 1913

1. n. A suffix forming adjectives and adverbs, and denoting likeness or resemblance.