(Employers may not begin the Form I-9 process until an individual accepts an offer of employment.) Forms I-9 must be kept for three years after the date of hire or one year after the date of the employee's termination, whichever is later.
Sine qua non (/ËsaÉªni kweÉª ËnÉn/; Latin: [Ësine kwaË ËnoËn]) or conditio sine qua non (plural: conditiones sine quibus non) is an indispensable and essential action, condition, or ingredient.
1 A sinusoid is a specific back-and-forth pattern (a sine or cosine wave), and 99% of the time, it refers to motion in one dimension.  A circle is a round, 2d pattern you probably know. If you enjoy using 10-dollar words to describe 10-cent ideas, you might call a circular path a complex sinusoid.