Identify a synonym for "happy".

The word "joyful" is a synonym for "happy" because both terms express a sense of delight, contentment, and positive emotion. They are used to convey a similar state of being, where one experiences pleasure or satisfaction. Synonyms are words that have closely related meanings, and in this case, "joyful" directly reflects the sentiment of happiness, enhancing the understanding of a positive emotional state.

The other choices do not convey the same emotional positivity: "sad" indicates a feeling of sorrow, "angry" describes a state of intense displeasure, and "discontent" reflects dissatisfaction or unhappiness, all contrasting with the meaning of "happy." Thus, "joyful" stands out as the appropriate synonym.