If you have the sound jian but not the character, here are the 4 characters read this way: 间 (jiān, space between, interval, room), 简 (jiǎn, simple, brief, terse; a bamboo writing slip), 见 (jiàn, to see, to meet, to appear), 件 (jiàn, item, piece, measure word). They split across 3 tones, so the tone is what separates them.