Cases of word usage

1) the parallel of latitude 23 degrees South (Capricorn)

2) a flat curve formed by cutting a cone along a line parallel to its side (parabola)

3) a four-sided plane figure whose opposite sides are parallel (parallelogram)

4) a group of professional workers in a business, school etc; a group of officers in the army; a set of five parallel lines on which notes are written (staff)

5) one of a set of rows (especially of seats) parallel to and rising one above another, e.g. in a theatre or stadium (tier)