Musical terms that determine the degree of loudness of the music, called dynamic shades (from the Greek word dynamicos - power, i.e. the power of the sound). In the notes you certainly saw these icons: pp, p, mp, mf, f, ff, dim, cresc. All of these are abbreviations of the names of dynamic shades. Let's see how they are fully pronounced and translated:
pp - pianissimo (pianissimo) - very quiet;
p - piano (piano) - quiet;
mp - mezzo piano (mezzo piano) - moderately quiet, a little louder than the piano;
mf - mezzo forte (mezzo Forte) - moderately loud, louder than mezzo piano;
f - forte (Forte) - loud;
ff - fortissimo (FF) - very loud.
Sometimes, more rarely, in the notes you can find such designations: ppp (piano pianissimo), Ruh-Roh. Or fff, (Forte-fortissimo), ffff. They mean very, very quiet, barely audible, very, very loudly.
Sign sf - sforzando (sforzando) indicates the selection of any note or chord.
Very often in the music and the words dim, diminuendo (diminuendo) or icon >pointing to a gradual weakening of the sound. Cresc. (crescendo), or icon < indicate, on the contrary, what is necessary to gradually increase the sound. Before designation cresc. sometimes put poco and poco (generation and generation) - little by little, little by little, gradually.
Of course, these words are found in other combinations. After gradually can not only enhance the sound, but to weaken it, to speed up or slow down the movement.
Instead diminuendo sometimes write morendo (Marengo) - fading. This definition means not only fading but also slowing down the pace. Approximately the same meaning has the word smorzando (smorzando) - muting, fading, weakening the sonority and slowing the pace.
You probably have heard the play "November" from the cycle "the seasons" by Tchaikovsky. It has the subtitle "the Troika". Begins is not very loud (mf) simple melody, like a Russian folk song. It grows, spreads, and now it sounds powerful, loud (f). The following musical episode, more lively and graceful imitates the sound of bells road. And then on the background of incessant ringing bells again there is the melody of the song - the quiet (R), then approaching and again disappearing in the distance (>), gradually fading.
P. I. Tchaikovsky. Times of the year. November