压 (yā) is a general verb meaning 'to press down' physically or 'to suppress' figuratively. Unlike 压缩 (yā suō 'compress'), which focuses on reducing volume/size, or 压迫 (yā pò 'oppress'), which implies sustained political/social force, 压 is broader and less specific — it can mean pressing a button, lowering your voice, or pressuring someone.