The Hebrew adjective sameach means joyful, glad, or merry — describing a person in a state of genuine joy, especially the joy that accompanies worship, celebration, and experiencing God's goodness. It is the adjectival form of samach (to rejoice).
Sameach describes the person fully alive to God's goodness. In Deuteronomy 16:15, the LORD commands Israel to be 'altogether joyful' during the feast — this is not a feeling to manufacture but a response to be cultivated in God's presence. The joy commanded in Scripture is not forced optimism but the natural overflow of a heart that has truly encountered divine grace. Nehemiah 8:10 — 'the joy of the LORD is your strength' — uses related vocabulary to assert that joy is not a luxury but a source of resilience. The sameach person is not naive about suffering (Psalm 137's lament sits near Psalm 133's joy) but has found a deeper gladness in God that circumstances cannot permanently extinguish.