"
Sacrament" means the visible sign of something holy-- that is, which brings us closer to God. The E. Orthodox also use, and prefer, the term "
Mystery" which has an even more profound connotation-- something forever incomprehensible to us which unites us, in a way (see link 1, below), with God.
Obviously, the ceremonies of the Church are sacraments/mysteries. BTW, the number seven as in "seven sacraments" is just a modern Sunday-school convention imported from western Scholastic and counter-reformation theology.
The holy fathers consider every ceremony and blessing of the Church a sacrament/mystery.
Man is also a sacrament/mystery in a way, and so is the rest of creation.
But the ultimate sacrament/mystery of all is, of course, God. He is a sacrament in that there's nothing holier than He. In Orthodoxy, He is also a unique, eternal mystery. I explain more in the following:
Link 1
Our "knowledge" of God depends on our spiritual state. For a related theological website, go here:
Link 2
The created world, including man, is also a sacrament/mystery. It is a sacrament because God made it and "it was good" (Genesis, ch. 1). Thus, even though it is fallen, it always has the potential for holiness. And, secretly sustaining it, and leading it to its ultimate sanctification at the end of time, are the uncreated energies of God (see link 1, above). It is a sacrament/mystery "in progress" as it were.
It is also a mystery, because knowledge of the true, fundamental nature of the world, including ourselves, depends-- ultimately-- not on outward (sensory) scientific knowledge; but on our spiritual state, which is a deeper form of "scientific"-- that is, directly perceived, first-hand-- knowledge. See the links below:
Link 3
(In the links below, "
theoria" refers to the spiritual vision attained by someone in the state of
theosis (divinization or sanctity), the goal and pinnacle of EO spirituality).
Link 4
(Below, note the "fifth theoria", "sixth theoria" and "seventh theoria").
Link 5