Letters that make closed interval
s, a, o, d, e, l, n, c, r, t, i, v are letters that make 'closed interval'
Words within closed interval
ER, RV, interval, os, OS, te, NT, VA, cl, SE, inter, ED, close, closed, in, AL, IN, Al, Cl, Er, In, Os, Se, Te, lose are words within 'closed interval'