three-line

One line would mean eighth-notes alternating. Two lines would mean sixteenths. Three lines means 32nds. In practical use, three lines means "fast notes, not necessarily 32nds". This is especially true in drum rolls.

Typically 3 slashes across the stem of a note is composer shorthand for tremolo.

Musical Line: A melodic statement which runs through a composition. This line (or voice) can be vocal or instrumental. Line or Phrase: A musical phrase or complete thought is often referred to as a line.

A triplet is written by putting a “3” over the top of the notes to show that 3 notes should fit in where there would normally only be 2. So in this example the “3” over the top of the crotchets means that 3 crotchets adds up to 2 beats instead of 3.

Equal sign with three lines, i.e. ≡ means identical to. This is similar to, but not exactly the same as, equals, i.e. =.

Triple “Triple” refers to the three beats per measure. “Triple” refers to the three beats per bar.

This is a triplet marker. If you tally up the note lengths in this bar, you'll see that they don't add up to 4/4. The crotchet and quaver between which the "3" is printed are supposed to be shorter than usual so that 3 rather than 2 notes to a crotchet are played.

A semiquaver is a musical note played for half the duration of a quaver. It has the time value of a sixteenth of a semibreve (whole note).

A double barline consists of two lines, both the width of single barlines, positioned half a space apart by default. It is often used to denote significant changes in the music, or to mark the placement of rehearsal marks, key signature changes, and tempo changes.

You now know that a staff is a graphical system used to read notes with five lines and four spaces. These lines and spaces house the notes of the musical alphabet: A, B, C, D, E, F and G. The treble clef symbol looks like this and signifies medium to high pitches being read on the staff.

In Western musical notation, the staff (US and UK) or stave (UK) (plural: staffs or staves) is a set of five horizontal lines and four spaces that each represent a different musical pitch or in the case of a percussion staff, different percussion instruments.

The Tripuṇḍra, three horizontal lines, on the forehead as well as other body parts are symbols during rites of passages, and for some a daily practice. These lines, states Antonio Rigopoulos, represent Shiva's threefold power of will (icchāśakti), knowledge (jñānaśakti), and action (kriyāśakti).