From the family of 'chordophone' instruments, along with the viola, the cello and the double bass. Before the mid-16th century, there had been the 'lira da braccio,' the 'rebec' and, of course, the 'fiddle.'

Already the "early violin proper...had four strings, lateral pegs, a waisted body and f-shaped sound holes...(but) the perfecting of the bow in the 19th century further increased (its) possibilities." (from Musical Instruments of the World,' Bantam Books)

Fragments from Wikipedia: "Legendary violin manufacturer Antonio Stradivari (b.1644-d.1737) probably served as a pupil in Niccolò Amati's workshop...In the past, instruments by Stradivari's teacher, Nicolo Amati, and an Austrian genius, Jacob Stainer, who might also have studied with Amati, were preferred for their subtle sweetness of tone.

(Cont.) "In 1680 Stradivari set up for himself in the Piazza San Domenico, Cremona, and his fame as an instrument-maker was soon established. Apart from violins, Stradivari also made harps, guitars, violas, and cellos more than 1,100 instruments in all, by current estimate. About 650 of these instruments survive today.

"He began to show his originality, and to make alterations in Amati's model. The arching was improved, the various degrees of thickness in the wood were more exactly determined, the formation of the scroll altered, and the varnish more highly coloured. His instruments are recognized by their inscription in Latin: Antonius Stradivarius Cremonensis Faciebat Anno [date] (Antonio Stradivari, Cremona, made in the year ...). It is generally acknowledged that his finest instruments were manufactured from 1698 to 1725 (peaking around 1715), exceeding in quality those manufactured between 1725 and 1730. After 1730, some of the instruments are signed Sotto la Desciplina d'Antonio Stradivari F. in Cremona [date], and were probably made by his sons, Omobono and Francesco.

(Cont.) "His instruments are regarded as amongst the finest stringed instruments ever created, are highly prized, and still played by professionals today. Only one other maker, Joseph Guarneri del Gesù, commands the same respect among violinists."

Improvements in violin making attempt to achieve tone that is more full and brilliant, which entail using "strings that are thinner and at greater tension, and a higher, more curved bridge that facilitates clean bowing." (From 'Musical Instruments of the World,' Bantam) On Bow action, the Bantam publication observes: "Different effects can be achieved by varying the method of bowing. The commonest method consists of smooth down-strokes and up-strokes, in which the bow is drwan across the strings from nut to point and back again. Other bowing methods include 'staccato' or detached strokes, 'hammered' strokes where each stroke is released forcefully and 'jeté' strokes where the bow is allowed to bounce across the strings."
And plucking the strings between the thumb and forefinger of the right hand produces 'pizzicato.'

There is plenty of instrumental virtuosity to be found in Bach's 'Partitas for violin, solo', and in Niccolo Paganini's 'Caprices.' Mozart's deceptively simple sonatas for violin and piano allow much in the enjoyment of either instrument. Renowned concertos for violin were written, one each mostly, by Beethoven, Brahms, Mendelssohn, Tchaikovsky, Saint-Saens, Sibelius, Bruch and Alban Berg; but and, very enjoyably, in Antonio Vivaldi's and Bach's own many concertos for string instruments.