Note grouping. A=Arsis, T=Thesis.^[1]

Binary and ternary rhythms and meter are said to originate in human movement.^[1] Inh.=Inhalation, Exh.=Exhalation.

In music and prosody, arsis and thesis refer to the stronger and weaker parts of a musical measure or poetic foot. Arsis and thesis were the raising and lowering of the foot in beating of time, or the raising and lowering of the voice in pitch or stress. Accordingly, in music and in Greek scansion arsis is an unaccented note (upbeat),^[2] but in Latin and modern poetry it is the stressed syllable (ictus).^[3]

Latin and English poetry

In Latin (and Greek) dactylic hexameter, the strong part of a foot is the first syllable always long and the weak part is what comes after two short syllables (dactyl: long short short) or one long syllable (spondee: long long). Because Classical poetry was not based on stress, the arsis is often not stressed; only consistent length distinguishes it.

• Arma virumque can , Troiae qu pr mus ab r s...
  Of arms and a man I sing, who first from the shores of Troy... Aeneid 1.1

In English, poetry is based on stress, and therefore arsis and thesis refer to the accented and unaccented parts of a foot.

Etymology

Ancient Greek rsis "lifting, removal, raising of foot in beating of time",^[4] from a r or ae r "I lift".^[5] The i in a r is a form of the present tense suffix y, which switched places with the r by metathesis.

Ancient Greek th sis "setting, placing, composition",^[6] from t th mi (from root / , the/th , with reduplication) "I put, set, place".^[7]

References