If responder jumps to 2NT over a 1/1 opener, it is J2NT asking opener to show a singleton or void. It shows 13+Points, support for opener's suit and is game forcing. Opener rebids as follows:

Opener	Responder	Opener's rebid shows		Responder
1	2NT!	3!	Max hand, 18+Points and strong suit but denies short suit	Either sign off, bid game, or look for slam
		3/3/3	Singleton or void in bid suit
		3NT!	Medium hand, 15-17 Points, denies short suit (artificial)
		4	Minimum hand and denies short suit
		4/4/4	Strong 5-card side suit

Oswald (Ozzie) Jacoby (1902 - 1984) - Ozzie Jacoby was one of the world's best players and writers for fifty years. In the '30s, Jacoby played on the famous Four Aces Team that won several national events. Ultimately he would win 30 national championships, his last at the age of 81. As a bridge columnist, he penned 10,000 articles. Jacoby was also an ardent patriot, serving in the armed forces in WWI (at 15), WW2 and the Korean War.