-ly

The suffix ''-ly'' in English is usually a contraction of ''-like'', similar to the Anglo-Saxon ''-lice'' and German ''-lich''. It is commonly added to an adjective to form an adverb, but in some cases it is used to form an adjective, such as ''ugly'' or ''manly''. When "-ly" is used to form an adjective, it is attached to a noun instead of an adjective (i.e., ''friendly'', ''lovely''). The adjective to which the suffix is added may have been lost from the language, as in the case of ''early'', in which the Anglo-Saxon word ''aer'' only survives in the poetic usage ''ere''.

Though the origin of the suffix is Germanic, it may now be added to adjectives of Latin origin, as in ''publicly''.

When the suffix is added to a word ending in the letter ''y'', the ''y'' before the suffix is replaced with the letter ''i'', as in ''happily'' (from ''happy''). This does not always apply in the case of monosyllabic words; for example, ''shy'' becomes ''shyly'' (but ''dry'' can become ''dryly'' or ''drily'', and ''gay'' becomes ''gaily''). Other examples are ''heavily'' (from ''heavy''), ''luckily'' (from ''lucky''), ''temporarily'' (from ''temporary''), ''easily'' (from ''easy''), ''emptily'' (from ''empty''), and ''funnily'' (from ''funny'').

When the suffix is added to a word ending in double ''l'', only ''y'' is added with no additional ''l''; for example, ''full'' becomes ''fully''. Note also ''wholly'' (from ''whole''), which may be pronounced either with a single ''l'' sound (like ''holy'') or with a doubled (geminate) ''l''.

When the suffix is added to an adjective ending in a vowel letter followed by the letter ''l'', it results in an adverb spelled with ''-lly,'' for example, the adverb ''centrally'' from the adjective ''central,'' but without a geminated l sound in pronunciation. Other examples are ''actually'', ''historically'', ''really'', ''carefully'', ''especially'', and ''usually''. When the suffix is added to a word ending in a consonant followed by ''le'' (pronounced as a syllabic ''l''), generally the mute ''e'' is dropped, the ''l'' loses its syllabic nature, and no additional ''l'' is added; this category is mostly composed of adverbs that end in ''-ably'' or ''-ibly'' (and correspond to adjectives ending in ''-able'' or ''-ible''), such as ''probably'', ''presumably'', ''visibly'', ''terribly'', ''horribly'' and ''possibly'', but it also includes other words such as ''nobly,'' ''feebly,'' ''simply'', ''doubly'', ''triply,'' ''quadriply'' and ''idly.'' However, there are a few words where this contraction is not always applied, such as ''brittlely.''

When ''-ly'' is added to an adjective ending ''-ic'', the adjective is usually first expanded by the addition of ''-al''. For example, there are adjectives ''historic'' and ''historical'', but the only adverb is ''historically''. Other examples are ''basically'', ''alphabetically'', ''scientifically'', ''chemically'', ''classically'', and ''astronomically''. There are a few exceptions such as ''publicly.''

Adjectives in ''-ly'' can form inflected comparative and superlative forms (such as ''friendlier, friendliest'', ''lovelier'', ''loveliest''), but most adverbs with this ending do not (a word such as ''sweetly'' uses the periphrastic forms ''more sweetly, most sweetly''). For more details see Adverbs and Comparison in the English grammar article.

The Libyan domain, .ly was used for domain hacks for this suffix.

There are some words that are neither adverbs nor adjectives, and yet end with ''-ly'', such as ''apply'', ''family'', ''supply''. There are also adverbs in English that do not end with ''-ly'', such as ''now'', ''then'', ''tomorrow'', ''today'', ''upstairs'', ''downstairs'', ''yesterday'', ''overseas'', ''behind'', ''already''. Provided by Wikipedia