[dawn] 
| 1. | the first appearance of daylight in the morning: Dawn broke over the valley. |
| 2. | the beginning or rise of anything; advent: the dawn of civilization. |
| 3. | to begin to grow light in the morning: The day dawned with a cloudless sky. |
| 4. | to begin to open or develop. |
| 5. | to begin to be perceived (usually fol. by on): The idea dawned on him. |
dawn on
Also, dawn upon. Become evident or understood, as in It finally dawned on him that he was expected to call them, or Around noon it dawned upon me that I had never eaten breakfast. This expression transfers the beginning of daylight to the beginning of a thought process. Harriet Beecher Stowe had it in Uncle Tom's Cabin (1852): "The idea that they had either feelings or rights had never dawned upon her." [Mid-1800s]