Sextile
A sextile is two bodies 60 degrees apart, in compatible elements, and it is the aspect of opportunity: a cooperation that is available but has to be taken up.
It joins fire with air or earth with water, the pairs that share a quality rather than an element, so the planets get on without being alike. That is why it is read as easy but not automatic.
The classical distinction between sextile and trine is one of degree and of effort. A trine hands you the result; a sextile hands you the chance. It is the aspect most often described as needing to be used, and the one most easily left unused.
Frequently asked
Is a sextile weaker than a trine?
Milder rather than weaker. It offers the same cooperation but expects you to act on it rather than receive it.
Why is it called the sixty and not the hexagon?
Because the aspects are named for the fraction of the circle they cut: a sixth of 360 degrees is 60.