The various classes of adverbs (AdvPs) enter a rigidly ordered sequence, which is the same across languages. And if one sets aside agreement and negation, the order of the head morphemes encoding the different types of functional notions in the clause (mood, modality, tense, aspect, and voice) is also rigidly fixed, and apparently invariant across languages. The two hierarchies (that of AdvPs, and that of functional heads) match systematically, from left to right.
Standardized
The various classes of adverbs (AdvPs) enter a rigidly ordered sequence, which is the same across languages. And if one sets aside agreement and negation, the order of the head morphemes encoding the different types of functional notions in the clause (mood, modality, tense, aspect, and voice) is also rigidly fixed, and apparently invariant across languages. The two hierarchies (that of AdvPs, and that of functional heads) match systematically, from left to right.
The universal hierarchy of clausal functional projections (Cinque 1999: 106):[frankly Mood_speech act [fortunately Mood_evaluative [allegedly Mood_evidential [probably Mod_epistemic [once T(Past)[then T(Future) [perhaps Mood_irrealis [necessarily Mod_necessity [possibly Mod_possibility [usually Asp_habitual [again Asp_repetitive(I) [often Asp_frequentative(I) [intentionally Mod_volitional [quickly Asp_celerative(I) [already T(Anterior) [no longer Asp_terminative [still Asp_continuative [always Asp_perfect(?) [just Asp_retrospective [soon Asp_proximative [briefly Asp_durative [characteristically(?) Asp_generic/progressive [almost Asp_prospective [completely Asp_SgCompletive(I) [tutto Asp_PlCompletive [well Voice [fast/early Asp_celerative(II) [again Asp_repetitive(II) [often Asp_frequentative(II) [completely Asp_SgCompletive(II)