Prayer — the specific word for directed prayer to God, as distinguished from general petition or intercession. Also used for a place of prayer (Acts 16:13). The core discipline of communion with God.
The NT treats proseuche as conversation with the Father — not merely petition but also praise, confession, and listening. Jesus' teaching on prayer (Matt 6, Luke 11) and Paul's exhortation to pray without ceasing (1 Thess 5:17) shape the whole NT ethic of prayer.
Philippians 4:6 offers anxiety's antidote: proseuche + deesis (supplication) + eucharistia (thanksgiving). The three together constitute full-orbed prayer — address to God, specific requests, and gratitude.