Fidelity means faithfulness and loyalty, especially staying true to your commitments and responsibilities. When someone shows fidelity in a friendship, they stand by their friend even when it's difficult. When parents promise to care for their children, they demonstrate fidelity by keeping that promise year after year.

The word appears in different contexts with slightly different shades of meaning. In marriage vows, fidelity means staying faithful to your spouse. In professional life, an employee shows fidelity to their company by working honestly and protecting confidential information. A dog's legendary fidelity to its owner means unwavering loyalty and devotion.

Fidelity also describes how accurately something reproduces or represents something else. A high-fidelity sound system (often called hi-fi) reproduces music so accurately that it sounds almost like hearing the original performance. When historians translate an ancient text, they aim for fidelity to the original meaning, without changing or adding things that weren't there.

The opposite of fidelity is infidelity, which means betraying trust or breaking faith with someone. Whether you're being faithful to a promise, a person, or the truth of something, fidelity means you can be counted on to do what you said you would do and be who you said you would be.