if p, then q” “p implies q”
“if p, q” “p only if q”
“p is sufficient for q” “a sufficient condition for q is p”
“q if p” “q whenever p”
“q when p” “q is necessary for p”
“a necessary condition for p is q” “q follows from p”
“q unless ¬p”
“p is necessary and sufficient for q”
“if p then q, and conversely”
“p iff q.