1. faithfulness to a person, group, belief, or the like.

2. the degree of accuracy of a measuring instrument or statistical model. For example, a representation derived from structural equation modeling that depicts a pattern of relationships between health attitudes and behaviors could be said to have fidelity if it accurately explains the variation and covariation in the data.

3. the degree of accuracy of sound or visual reproduction in an electronic device (e.g., a sound system, television).