The term "good night" in this poem is a euphemism for death. In this passionate and heartfelt poem, Thomas urges his father to fight against dying.

While other poems might recommend people to quietly accept death and to embrace the passage to the other side, Thomas does the opposite. He tells his father repeatedly to "rage" against death as long as possible.

Because the speaker is so adamant in urging his father to fight hard against death and not go quietly, the term "good night" for death becomes ironic. It can't be that good a night if the father is told to struggle and kick against it with all his strength.

The poem, is in fact, an affirmation of life on earth and of living as fully as possible to the very end. As the speaker says, "Rage, rage against the dying of the light."

In Dylan Thomas' poem, "Do Not Go Gentle Into that Good Night," the words "good night" mean death. The poet begins the poem with these words, and the line, in which they are written, is repeated at the end of stanzas two and four. Finally, the words are repeated at the end of the poem in line eighteen. This repetition shows the importance of plea of the speaker to his dying elderly father. The author is begging; he is saying do not give up easily at the time of death even though in certain situations death may be a relief from suffering. We say “good night” when putting a child to bed, when leaving someone in the evening, or as a simple wish to another person as they go to sleep. But in this poem the author is using the words metaphorically comparing a “good night” to death.