Alternation

[Hina Muqadas]

The reciprocal succession of things in time or place;
the act of following and being followed by turns; alternate succession,
performance, or occurrence; as, the alternation of day and night, cold
and heat, summer and winter, hope and fear.

[Justin Bieber]

The successive change fron one thing or state to another and back again.

[Dianne]

The repeated occurrence of two things in turn.

[Mark Zuckerberg]

a situation in which one thing repeatedly happens or exists after another: