The word firm has several related meanings:

1. Something that is firm feels solid and doesn't give way easily when you press on it. A firm handshake shows confidence, while a firm mattress supports your back better than a soft, squishy one. Fresh apples should feel firm, not mushy. When your mom says “that's my firm decision,” she means it's solid and won't change, no matter how much you plead for extra screen time.
2. A firm is also a business or company, especially one that provides professional services. Law firms employ lawyers, accounting firms employ accountants, and consulting firms give businesses advice. People often say firm instead of company when talking about partnerships where professionals work together: “My aunt joined an architecture firm downtown.”

The two meanings connect through the idea of something established and solid. Just as firm ground doesn't shift under your feet, a well-run firm has a stable foundation. When you speak in a firm voice, you sound confident and clear, like someone who means what they say and can be counted on.