Solution
= Solution
The arcs $\alpha$ and $\beta$ bound a <bigon formed by two arcs>[bigon] if there are subarcs with common endpoints whose union is the boundary of an embedded disc and whose interiors are disjoint. They are in <minimal position of curves or arcs>[minimal position] if $|\alpha\cap\beta|$ is the least possible intersection count among proper arcs isotopic to $\alpha$ and $\beta$ relative to their ends.