(Pros.)
(a)
That part of a foot where the ictus is put, or which is distinguished from the rest (known as the thesis) of the foot by a greater stress of voice.
(b)
That elevation of voice now called metrical accentuation, or the rhythmic accent. Note: It is uncertain whether the arsis originally consisted in a higher musical tone, greater volume, or longer duration of sound, or in all combined.