MEASURE, in a legal and commercial sense, denotes a certain quantity or proportion of any thing bought, sold, valued, or the like. See Weights and Measures. Measure is also used to signify the cadence and time observed in poetry, dancing, and music, in order to render them regular and agreeable.

The different measures or metres in poetry, are the different manners of ordering and combining the quantities, or the long and short syllables. Thus, hexameter, pentameter, iambic, sapphic, and other verses, consist of different measures.

In English verses, the measures are extremely various and arbitrary, every poet being at liberty to introduce any new form that he pleases. The most usual are the heroic, generally consisting of five long and five short syllables; verses of four feet; and verses of three feet and a caesura, or single syllable.

The ancients, by variously combining and transposing their quantities, made a vast variety of different measures. Of words, or rather feet of two syllables, they formed a spondee, consisting of two long syllables; a pyrrhic, of two short syllables; a trochee, of a long and a short syllable; and an iambic, of a short and a long syllable.

Of their feet of three syllables they formed a molossus, consisting of three long syllables; a tribrachys, of three short syllables; a dactyl, of one long and two short syllables; and an anapaest, of two short and one long syllable. The Greek poets contrived one hundred and twenty-four different combinations or measures; under as many different names, from feet of two syllables to those of six.

Measure of an angle, is an arch described from the vertex in any place between its legs. Hence angles are distinguished by the ratio of the arches, described from the vertex between the legs to the peripheries. Angles, then, are distinguished by those arches; and the arches are distinguished[7:14:345] by their ratio to the periphery. Thus an angle is said to be as many degrees as there are in the said arch.

Measure of a solid, is a cube, the side of which is an inch, a foot, or a yard, or any other determinate length. In geometry it is a cubic perch, divided into cubic feet, digits, &c.

Measure of velocity, in Mechanics, is the space which is passed over by a moving body in a given time. To measure a velocity, therefore, the space must be divided into as many equal parts as the time is conceived to be divided into; and the quantity of space answering to such a part of time is the measure of the velocity.

Measure, in Geometry, denotes any quantity assumed as one, or unity, to which the ratio of the other homogeneous or similar quantities is expressed, numerically or otherwise.

Measure, in Music, the interval or space of time which the person who beats time takes between the rising and falling of his hand or foot, in order to conduct the movement, sometimes quicker, and sometimes slower, according to the kind of music, or the subject which is sung or played. The measure is that which regulates the time we are to dwell on each note.

The ordinary or common measure is one second, or the sixtieth part of a minute, which is nearly the space between the beats of the pulse or heart; the systole, or contraction of the heart, answering to the elevation of the hand; and its diastole, or dilatation, to the letting it fall. The measure usually takes up the space which a pendulum of two feet and a half long employs in making a swing or vibration. The measure is regulated according to the different quality or value of the notes in the piece, by which the time that each note is to occupy is expressed. The semibreve, for instance, holds one rise and one fall; and this is called the measure or whole measure, sometimes the measure note or time note; the minim, one rise, or one fall; and the crotchet, half a rise, or half a fall, there being four crotchets in a full measure.

Measure Einary, or Double, is that in which the rise and fall of the hand are equal.

Measure Ternary, or Triple, is that in which the fall is double of the rise; or where two minims are played during a fall, and but one in the rise. To this purpose, the number 3 is placed at the beginning of the lines, when the measure is intended to be triple; and a C, when the measure is to be common or double.