A Dictionary of Music and Musicians/Sforzando
SFORZANDO, SFORZATO, 'forced'; a direction usually found in its abbreviated form sf. or sfz. referring to single notes or groups of notes which are to be especially emphasized. It is nearly equivalent to the accent 
, but is less apt to be overlooked in performance, and is therefore used in all important passages—as for instance, in certain canons where the leading part has a strongly accented note which is to be brought out with equal force in the imitating part. Good instances occur in Beethoven's Sonata for violin and piano in C minor, Op. 30, No. 2, in the trio of the Scherzo; in Schumann's Etudes Symphoniques Variations [App. p.792 "Variation 3"], etc.
, but is less apt to be overlooked in performance, and is therefore used in all important passages—as for instance, in certain canons where the leading part has a strongly accented note which is to be brought out with equal force in the imitating part. Good instances occur in Beethoven's Sonata for violin and piano in C minor, Op. 30, No. 2, in the trio of the Scherzo; in Schumann's Etudes Symphoniques Variations [App. p.792 "Variation 3"], etc.
[ J. A. F. M. ]