1) Fewness 2) Noteworthy scarcity 3) Rareness 4) Rarity 5) Scarceness 6) Scarcity 7) Shortage 8) State of being infrequent 9) Uncommonness Found on https://www.crosswordclues.com/clue/infrequency
• (n.) The state of rarely occuring; uncommonness; rareness; as, the infrquence of his visits. • (n.) The state of not being frequented; solitude; isolation; retirement; seclusion. Found on http://thinkexist.com/dictionary/meaning/infrequency/