Bridge Conventions:
After an opponent opens a big 1♣ or a big 2♣, suction intervention uses a bid of any suit (at any level) for a 1-suiter that is one step above what the intervenor actually bid. But occasionally the intervenor will not have a 1-suiter but will rather have a 2-suiter: the 2 touching suits that are immediately above that implied 1-suiter. A double can be used similarly to show a ♦ 1-suiter or a major 2-suiter. Any NT bid is used for 2 non-touching suits - either the "round" suits or the "pointed" suits.
double =
♦ 1-suiter or major 2-suiter
♦ bid (any level) =
♥ 1-suiter or black 2-suiter
♥ bid (any level) =
♠ 1-suiter or minor 2-suiter
♠ bid (any level) =
♣ 1-suiter or red 2-suiter
♣ bid (any level) =
♦ 1-suiter or major 2-suiter
NT bid (any level) =
nontouching 2-suiter: either the "round" suits (♥ & ♣), else the "pointed" suits (♠ & ♦)