(1) Fellowship between Christians.
(2) Group or denomination of Christians sharing a common creed.
(3) The sacrament of the Eucharist.
Communion in One Kind
Catholic practice at the Eucharist of offering the consecrated bread but not the wine to laypeople. Only the priest took the Communion in 'both kinds'. It was, however, common for the laity to partake in wine at the absolution of sin.
Communion in Both Kinds
Protestant practice of offering both consecrated bread and wine to all communicants, lay and spiritual.