Select the most appropriate synonym of the given word.
Mourn

To find the most appropriate synonym for the given word, let's analyze its meaning and the meanings of the provided options:

Mourn: This verb means to feel or express great sadness or sorrow, especially over someone's death or a significant loss.

Now, let's examine the options:
1. Dread: To anticipate with great apprehension or fear.
2. Amuse: To cause someone to find something funny or entertaining.
3. Grieve: To feel intense sorrow or deep grief, especially after a loss. This aligns perfectly with the definition of "mourn".
4. Approve: To officially agree to or accept as satisfactory.

Therefore, the word that is closest in meaning (synonym) to "Mourn" is Grieve.