"o swear not by the moon, the inconstant moon"
-moon associated with changeability
-Juliet is urging Romeo to make a vow that is permanent and certain. The moon’s inconstancy is a metaphor for something that fluctuates This is because, due to uncertainty surrounding their relationship (the feud between their families, the secrecy of their love), she longs for something stable and lasting.
-While Romeo is impulsive and idealistic, Juliet is more rational and grounded in this moment.
-tragic irony :Juliet wishes for something constant, but their love will ultimately prove to be fleeting.