In short

An adverb describes the verb, so unlike an adjective it never changes: Lei canta bene, Loro cantano bene. To build one from an adjective, take the feminine singular and add -mente: lenta -> lentamente. And the default position is right after the verb, not before it: Bevo sempre il caffè, never Sempre bevo il caffè.

The rule

Adverbs answer how, when, where and how much. The whole topic is three habits: know the classes, build the -mente forms, and put them in the right slot.

Step 1 - Recognise the four classes. Most of these you have met since A1; the point here is that they are one family with one shared property - they are invariable.

• Manner (how?): bene, male, volentieri, insieme, piano, forte, così, plus every -mente form.
• Time (when?): già, ancora, sempre, mai, spesso, subito, presto, tardi, adesso, ieri, oggi, domani, poi.
• Place (where?): qui/qua, lì/là, sopra, sotto, dentro, fuori, vicino, lontano, davanti, dietro.
• Quantity (how much?): molto, poco, troppo, tanto, abbastanza, quasi, più, meno.

Step 2 - Build the -mente adverb. This is the productive machine: it turns almost any adjective into an adverb, and it has exactly two rules.

• Rule A - go through the feminine singular. lento -> lenta -> lentamente, vero -> vera -> veramente, raro -> rara -> raramente. Adjectives that end in -e have one form for both genders, so you simply add -mente: veloce -> velocemente, semplice -> semplicemente, forte -> fortemente.
• Rule B - adjectives ending in -le or -re drop the final -e. facile -> facilmente, difficile -> difficilmente, gentile -> gentilmente, normale -> normalmente, regolare -> regolarmente, particolare -> particolarmente. There is no facilemente.

Rule B only applies when the l or r follows a vowel. That is why folle -> follemente keeps its -e: the l follows another l.

Step 3 - Do not confuse the adjective with the adverb. An adjective describes a noun and agrees with it; an adverb describes a verb and is frozen. The pair that catches everyone is buono (adjective) vs bene (adverb), and cattivo vs male.

• Il caffè è buono. - the coffee is good (adjective, agrees: buona, buoni).
• Il caffè si beve bene qui. / Sto bene. - adverb, always bene.

There is one important exception to memorise rather than reason about: a small set of adjectives is used as an adverb, unchanged, in fixed pairs - parla piano, parla forte, vai veloce, costa caro, lavora sodo. Parla veloce and parla velocemente are both correct; veloce here is the informal spoken option, velocemente the neutral written one. This licence does not extend to buono: parla buono is simply wrong.

Step 4 - Place the adverb. Italian is stricter than English here.

• Simple tense: after the verb. Mangio spesso la pasta. English says “I often eat pasta”; Italian does not put the adverb before the verb.
• Compound tense: short time adverbs go inside. già, mai, sempre, ancora and più sit between the auxiliary and the participle: Ho già mangiato, Non ho mai visto, Non è ancora arrivato. See Passato prossimo for the auxiliary itself.
• Long -mente adverbs go after the participle: Ho parlato chiaramente, Ha guidato lentamente.
• Sentence adverbs go first, before everything, and comment on the whole sentence: Purtroppo non posso venire., Generalmente mangio a casa.

Step 5 - Learn the four irregular grades. Four adverbs do not take più to form their comparative - they have their own word.

• bene -> meglio, male -> peggio, molto -> di più, poco -> di meno.
• The trap: meglio and peggio are adverbs, so they modify a verb (Sto meglio, Scrive peggio di me). When you are describing a noun after essere, you need the adjectives migliore and peggiore: Questo vino è migliore. The full comparison system is in Comparatives and superlatives.

Forms & patterns

Building the -mente adverb:

The four classes at a glance:

Adjective (agrees) vs adverb (frozen):

The irregular grades:

Position, by tense:

Examples

Common mistakes

• Sempre bevo il caffè al bar. -> Bevo sempre il caffè al bar. English puts the adverb before the verb; Italian puts it after. Sentence-initial is reserved for comment adverbs like purtroppo.
• Ho mangiato già. -> Ho già mangiato. In a compound tense the short adverbs già, mai, sempre, ancora, più are sandwiched between the auxiliary and the participle.
• Lei canta buono. -> Lei canta bene. buono is an adjective - it needs a noun (un caffè buono). To describe how someone sings you need the adverb bene.
• Si risolve facilemente. -> Si risolve facilmente. Adjectives in -le and -re drop the final -e before -mente: facile -> facilmente, regolare -> regolarmente.
• È un film meglio dell’altro. -> È un film migliore dell’altro. meglio is an adverb and modifies a verb (Sto meglio). Describing a noun takes the adjective migliore. After essere you will also hear Questo film è meglio in casual speech, but migliore is the standard choice.

Tips

• The -mente recipe is “feminine first”. Never build from the masculine: think lenta, then say lentamente. Adjectives in -e have no separate feminine, so there is nothing to change - veloce -> velocemente.
• L and R lose their E. That single line is all of Rule B: facile -> facilmente, regolare -> regolarmente, gentile -> gentilmente. It is also why facilemente sounds instantly foreign.
• Ask “how does he do it?” If the answer describes the action, use bene / male / -mente. If it describes the thing, use buono / cattivo and make it agree - see Adjectives: agreement and position.
• Sto meglio, ma il vino è migliore. Learn this one sentence by heart: it stores the adverb and the adjective in their natural slots, and it settles the most common B1 confusion for good.