 Major arc

In a circle-method problem of scale $n$, major arcs are neighborhoods of reduced rational points $a/q$ with small denominator, where the relevant exponential sum is approximated using distribution in residue classes. For the three-prime problem one may take $q\le (\log n{)}^B$ and $|\theta -a/q|\le (\log n{)}^B/n$, with suitably fixed $B$.