ir-ir- /ɪ/ prefix 
used instead of in- before the letter r SYN not: 
irregular (=not regular)
used instead of in- before the letter r SYN not: irregular (=not regular)- concentrated
- concentration
- concentration camp
- concentric
- concept
- conception
- conceptual
- conceptual art
- conceptualization
- conceptualize
- conceptually
- concern
- concerned
- concerning
- concert
- concerted
- concertedly
- concertgoer
- concert hall
- concertina
- concertmaster
- concerto
- concession
- concessionaire
- concessionary