Patanjali's yoga sutras

देशबन्धश्चित्तस्य धारणा ॥ ३.१ ॥

3.1 deśabandhaścittasya dhāraṇā

• desha = place, object, point, spot
• bandhah = binding to, holding, fixing, uniting
• chittasya = of the mind, consciousness
• dharana = concentration, focusing, directing attention

Focusing your attention on one thing is concentration .